687 lines
19 KiB
Markdown
687 lines
19 KiB
Markdown
# Vue
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For more complex frontend features, we recommend using Vue.js. It shares
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some ideas with React.js as well as Angular.
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To get started with Vue, read through [their documentation][vue-docs].
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## When to use Vue.js
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We recommend using Vue for more complex features. Here are some guidelines for when to use Vue.js:
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- If you are starting a new feature or refactoring an old one that highly interacts with the DOM;
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- For real time data updates;
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- If you are creating a component that will be reused elsewhere;
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## When not to use Vue.js
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We don't want to refactor all GitLab frontend code into Vue.js, here are some guidelines for
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when not to use Vue.js:
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- Adding or changing static information;
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- Features that highly depend on jQuery will be hard to work with Vue.js;
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- Features without reactive data;
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As always, the Frontend Architectural Experts are available to help with any Vue or JavaScript questions.
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## Vue architecture
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All new features built with Vue.js must follow a [Flux architecture][flux].
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The main goal we are trying to achieve is to have only one data flow and only one data entry.
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In order to achieve this goal, you can either use [vuex](#vuex) or use the [store pattern][state-management], explained below:
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Each Vue bundle needs a Store - where we keep all the data -,a Service - that we use to communicate with the server - and a main Vue component.
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Think of the Main Vue Component as the entry point of your application. This is the only smart
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component that should exist in each Vue feature.
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This component is responsible for:
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1. Calling the Service to get data from the server
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1. Calling the Store to store the data received
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1. Mounting all the other components
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You can also read about this architecture in vue docs about [state management][state-management]
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and about [one way data flow][one-way-data-flow].
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### Components, Stores and Services
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In some features implemented with Vue.js, like the [issue board][issue-boards]
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or [environments table][environments-table]
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you can find a clear separation of concerns:
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```
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new_feature
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├── components
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│ └── component.js.es6
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│ └── ...
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├── store
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│ └── new_feature_store.js.es6
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├── service
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│ └── new_feature_service.js.es6
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├── new_feature_bundle.js.es6
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```
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_For consistency purposes, we recommend you to follow the same structure._
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Let's look into each of them:
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### A `*_bundle.js` file
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This is the index file of your new feature. This is where the root Vue instance
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of the new feature should be.
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The Store and the Service should be imported and initialized in this file and
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provided as a prop to the main component.
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Don't forget to follow [these steps.][page_specific_javascript]
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### Bootstrapping Gotchas
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#### Providing data from Haml to JavaScript
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While mounting a Vue application may be a need to provide data from Rails to JavaScript.
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To do that, provide the data through `data` attributes in the HTML element and query them while mounting the application.
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_Note:_ You should only do this while initing the application, because the mounted element will be replaced with Vue-generated DOM.
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The advantage of providing data from the DOM to the Vue instance through `props` in the `render` function
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instead of querying the DOM inside the main vue component is that makes tests easier by avoiding the need to
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create a fixture or an HTML element in the unit test. See the following example:
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```javascript
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// haml
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.js-vue-app{ data: { endpoint: 'foo' }}
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document.addEventListener('DOMContentLoaded', () => new Vue({
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el: '.js-vue-app',
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data() {
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const dataset = this.$options.el.dataset;
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return {
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endpoint: dataset.endpoint,
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};
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},
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render(createElement) {
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return createElement('my-component', {
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props: {
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endpoint: this.isLoading,
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},
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});
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},
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}));
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```
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#### Accessing the `gl` object
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When we need to query the `gl` object for data that won't change during the application's lyfecyle, we should do it in the same place where we query the DOM.
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By following this practice, we can avoid the need to mock the `gl` object, which will make tests easier.
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It should be done while initializing our Vue instance, and the data should be provided as `props` to the main component:
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##### example:
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```javascript
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document.addEventListener('DOMContentLoaded', () => new Vue({
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el: '.js-vue-app',
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render(createElement) {
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return createElement('my-component', {
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props: {
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username: gon.current_username,
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},
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});
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},
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}));
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```
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### A folder for Components
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This folder holds all components that are specific of this new feature.
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If you need to use or create a component that will probably be used somewhere
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else, please refer to `vue_shared/components`.
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A good thumb rule to know when you should create a component is to think if
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it will be reusable elsewhere.
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For example, tables are used in a quite amount of places across GitLab, a table
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would be a good fit for a component. On the other hand, a table cell used only
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in one table would not be a good use of this pattern.
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You can read more about components in Vue.js site, [Component System][component-system]
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#### Components Gotchas
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1. Using SVGs in components: To use an SVG in a template we need to make it a property we can access through the component.
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A `prop` and a property returned by the `data` functions require `vue` to set a `getter` and a `setter` for each of them.
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The SVG should be a computed property in order to improve performance, note that computed properties are cached based on their dependencies.
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```javascript
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// bad
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import svg from 'svg.svg';
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data() {
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return {
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myIcon: svg,
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};
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};
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// good
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import svg from 'svg.svg';
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computed: {
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myIcon() {
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return svg;
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}
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}
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```
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### A folder for the Store
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The Store is a class that allows us to manage the state in a single
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source of truth. It is not aware of the service or the components.
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The concept we are trying to follow is better explained by Vue documentation
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itself, please read this guide: [State Management][state-management]
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### A folder for the Service
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The Service is a class used only to communicate with the server.
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It does not store or manipulate any data. It is not aware of the store or the components.
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We use [axios][axios] to communicate with the server.
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Refer to [axios](axios.md) for more details.
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Axios instance should only be imported in the service file.
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```javascript
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import axios from 'javascripts/lib/utils/axios_utils';
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```
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### End Result
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The following example shows an application:
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```javascript
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// store.js
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export default class Store {
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/**
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* This is where we will iniatialize the state of our data.
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* Usually in a small SPA you don't need any options when starting the store. In the case you do
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* need guarantee it's an Object and it's documented.
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*
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* @param {Object} options
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*/
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constructor(options) {
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this.options = options;
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// Create a state object to handle all our data in the same place
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this.todos = []:
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}
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setTodos(todos = []) {
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this.todos = todos;
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}
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addTodo(todo) {
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this.todos.push(todo);
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}
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removeTodo(todoID) {
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const state = this.todos;
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const newState = state.filter((element) => {element.id !== todoID});
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this.todos = newState;
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}
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}
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// service.js
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import axios from 'javascripts/lib/utils/axios_utils'
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export default class Service {
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constructor(options) {
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this.todos = axios.create({
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baseURL: endpoint.todosEndpoint
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});
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}
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getTodos() {
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return this.todos.get();
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}
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addTodo(todo) {
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return this.todos.put(todo);
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}
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}
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// todo_component.vue
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<script>
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export default {
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props: {
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data: {
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type: Object,
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required: true,
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},
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}
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}
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</script>
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<template>
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<div>
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<h1>
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Title: {{data.title}}
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</h1>
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<p>
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{{data.text}}
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</p>
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</div>
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</template>
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// todos_main_component.vue
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<script>
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import Store from 'store';
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import Service from 'service';
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import TodoComponent from 'todoComponent';
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export default {
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/**
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* Although most data belongs in the store, each component it's own state.
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* We want to show a loading spinner while we are fetching the todos, this state belong
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* in the component.
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*
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* We need to access the store methods through all methods of our component.
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* We need to access the state of our store.
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*/
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data() {
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const store = new Store();
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return {
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isLoading: false,
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store: store,
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todos: store.todos,
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};
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},
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components: {
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todo: TodoComponent,
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},
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created() {
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this.service = new Service('todos');
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this.getTodos();
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},
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methods: {
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getTodos() {
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this.isLoading = true;
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this.service.getTodos()
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.then(response => response.json())
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.then((response) => {
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this.store.setTodos(response);
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this.isLoading = false;
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})
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.catch(() => {
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this.isLoading = false;
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// Show an error
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});
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},
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addTodo(todo) {
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this.service.addTodo(todo)
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then(response => response.json())
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.then((response) => {
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this.store.addTodo(response);
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})
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.catch(() => {
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// Show an error
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});
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}
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}
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}
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</script>
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<template>
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<div class="container">
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<div v-if="isLoading">
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<i
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class="fa fa-spin fa-spinner"
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aria-hidden="true" />
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</div>
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<div
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v-if="!isLoading"
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class="js-todo-list">
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<template v-for='todo in todos'>
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<todo :data="todo" />
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</template>
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<button
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@click="addTodo"
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class="js-add-todo">
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Add Todo
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</button>
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</div>
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<div>
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</template>
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// bundle.js
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import todoComponent from 'todos_main_component.vue';
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new Vue({
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el: '.js-todo-app',
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components: {
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todoComponent,
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},
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render: createElement => createElement('todo-component' {
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props: {
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someProp: [],
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}
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}),
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});
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```
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The [issue boards service][issue-boards-service]
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is a good example of this pattern.
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## Style guide
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Please refer to the Vue section of our [style guide](style_guide_js.md#vue-js)
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for best practices while writing your Vue components and templates.
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## Testing Vue Components
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Each Vue component has a unique output. This output is always present in the render function.
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Although we can test each method of a Vue component individually, our goal must be to test the output
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of the render/template function, which represents the state at all times.
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Make use of Vue Resource Interceptors to mock data returned by the service.
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Here's how we would test the Todo App above:
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```javascript
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import component from 'todos_main_component';
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describe('Todos App', () => {
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it('should render the loading state while the request is being made', () => {
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const Component = Vue.extend(component);
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const vm = new Component().$mount();
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expect(vm.$el.querySelector('i.fa-spin')).toBeDefined();
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});
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describe('with data', () => {
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// Mock the service to return data
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const interceptor = (request, next) => {
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next(request.respondWith(JSON.stringify([{
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title: 'This is a todo',
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body: 'This is the text'
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}]), {
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status: 200,
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}));
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};
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let vm;
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beforeEach(() => {
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Vue.http.interceptors.push(interceptor);
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const Component = Vue.extend(component);
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vm = new Component().$mount();
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});
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afterEach(() => {
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Vue.http.interceptors = _.without(Vue.http.interceptors, interceptor);
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});
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it('should render todos', (done) => {
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setTimeout(() => {
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expect(vm.$el.querySelectorAll('.js-todo-list div').length).toBe(1);
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done();
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}, 0);
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});
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});
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describe('add todo', () => {
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let vm;
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beforeEach(() => {
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const Component = Vue.extend(component);
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vm = new Component().$mount();
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});
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it('should add a todos', (done) => {
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setTimeout(() => {
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vm.$el.querySelector('.js-add-todo').click();
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// Add a new interceptor to mock the add Todo request
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Vue.nextTick(() => {
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expect(vm.$el.querySelectorAll('.js-todo-list div').length).toBe(2);
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});
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}, 0);
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});
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});
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});
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```
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#### `mountComponent` helper
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There is a helper in `spec/javascripts/helpers/vue_mount_component_helper.js` that allows you to mount a component with the given props:
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```javascript
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import Vue from 'vue';
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import mountComponent from 'helpers/vue_mount_component_helper.js'
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import component from 'component.vue'
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const Component = Vue.extend(component);
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const data = {prop: 'foo'};
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const vm = mountComponent(Component, data);
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```
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#### Test the component's output
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The main return value of a Vue component is the rendered output. In order to test the component we
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need to test the rendered output. [Vue][vue-test] guide's to unit test show us exactly that:
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### Stubbing API responses
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Refer to [mock axios](axios.md#mock-axios-response-on-tests)
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## Vuex
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To manage the state of an application you may use [Vuex][vuex-docs].
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_Note:_ All of the below is explained in more detail in the official [Vuex documentation][vuex-docs].
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### Separation of concerns
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Vuex is composed of State, Getters, Mutations, Actions and Modules.
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When a user clicks on an action, we need to `dispatch` it. This action will `commit` a mutation that will change the state.
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_Note:_ The action itself will not update the state, only a mutation should update the state.
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#### File structure
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When using Vuex at GitLab, separate this concerns into different files to improve readability. If you can, separate the Mutation Types as well:
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```
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└── store
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├── index.js # where we assemble modules and export the store
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├── actions.js # actions
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├── mutations.js # mutations
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├── getters.js # getters
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└── mutation_types.js # mutation types
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```
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The following examples show an application that lists and adds users to the state.
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##### `index.js`
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This is the entry point for our store. You can use the following as a guide:
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```javascript
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import Vue from 'vue';
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import Vuex from 'vuex';
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import * as actions from './actions';
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import * as mutations from './mutations';
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Vue.use(Vuex);
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export default new Vuex.Store({
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actions,
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getters,
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state: {
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users: [],
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},
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});
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```
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_Note:_ If the state of the application is too complex, an individual file for the state may be better.
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#### `actions.js`
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An action commits a mutatation. In this file, we will write the actions that will call the respective mutation:
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```javascript
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import * as types from './mutation-types'
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export const addUser = ({ commit }, user) => {
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commit(types.ADD_USER, user);
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};
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```
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To dispatch an action from a component, use the `mapActions` helper:
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```javascript
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import { mapActions } from 'vuex';
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{
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methods: {
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...mapActions([
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'addUser',
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]),
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onClickUser(user) {
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this.addUser(user);
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},
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},
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};
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```
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#### `getters.js`
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Sometimes we may need to get derived state based on store state, like filtering for a specific prop. This can be done through the `getters`:
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```javascript
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// get all the users with pets
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export getUsersWithPets = (state, getters) => {
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return state.users.filter(user => user.pet !== undefined);
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};
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```
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To access a getter from a component, use the `mapGetters` helper:
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```javascript
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import { mapGetters } from 'vuex';
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{
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computed: {
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...mapGetters([
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'getUsersWithPets',
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]),
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},
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};
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```
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#### `mutations.js`
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The only way to actually change state in a Vuex store is by committing a mutation.
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```javascript
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import * as types from './mutation-types'
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export default {
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[types.ADD_USER](state, user) {
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state.users.push(user);
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},
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};
|
|
```
|
|
|
|
#### `mutations_types.js`
|
|
From [vuex mutations docs][vuex-mutations]:
|
|
> It is a commonly seen pattern to use constants for mutation types in various Flux implementations. This allows the code to take advantage of tooling like linters, and putting all constants in a single file allows your collaborators to get an at-a-glance view of what mutations are possible in the entire application.
|
|
|
|
```javascript
|
|
export const ADD_USER = 'ADD_USER';
|
|
```
|
|
|
|
### How to include the store in your application
|
|
The store should be included in the main component of your application:
|
|
```javascript
|
|
// app.vue
|
|
import store from 'store'; // it will include the index.js file
|
|
|
|
export default {
|
|
name: 'application',
|
|
store,
|
|
...
|
|
};
|
|
```
|
|
|
|
### Vuex Gotchas
|
|
1. Avoid calling a mutation directly. Always use an action to commit a mutation. Doing so will keep consistency through out the application. From Vuex docs:
|
|
|
|
> why don't we just call store.commit('action') directly? Well, remember that mutations must be synchronous? Actions aren't. We can perform asynchronous operations inside an action.
|
|
|
|
```javascript
|
|
// component.vue
|
|
|
|
// bad
|
|
created() {
|
|
this.$store.commit('mutation');
|
|
}
|
|
|
|
// good
|
|
created() {
|
|
this.$store.dispatch('action');
|
|
}
|
|
```
|
|
1. When possible, use mutation types instead of hardcoding strings. It will be less error prone.
|
|
1. The State will be accessible in all components descending from the use where the store is instantiated.
|
|
|
|
### Testing Vuex
|
|
#### Testing Vuex concerns
|
|
Refer to [vuex docs][vuex-testing] regarding testing Actions, Getters and Mutations.
|
|
|
|
#### Testing components that need a store
|
|
Smaller components might use `store` properties to access the data.
|
|
In order to write unit tests for those components, we need to include the store and provide the correct state:
|
|
|
|
```javascript
|
|
//component_spec.js
|
|
import Vue from 'vue';
|
|
import store from './store';
|
|
import component from './component.vue'
|
|
|
|
describe('component', () => {
|
|
let vm;
|
|
let Component;
|
|
|
|
beforeEach(() => {
|
|
Component = Vue.extend(issueActions);
|
|
});
|
|
|
|
afterEach(() => {
|
|
vm.$destroy();
|
|
});
|
|
|
|
it('should show a user', () => {
|
|
const user = {
|
|
name: 'Foo',
|
|
age: '30',
|
|
};
|
|
|
|
// populate the store
|
|
store.dipatch('addUser', user);
|
|
|
|
vm = new Component({
|
|
store,
|
|
propsData: props,
|
|
}).$mount();
|
|
});
|
|
});
|
|
```
|
|
|
|
[vue-docs]: http://vuejs.org/guide/index.html
|
|
[issue-boards]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/app/assets/javascripts/boards
|
|
[environments-table]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/app/assets/javascripts/environments
|
|
[page_specific_javascript]: https://docs.gitlab.com/ce/development/frontend.html#page-specific-javascript
|
|
[component-system]: https://vuejs.org/v2/guide/#Composing-with-Components
|
|
[state-management]: https://vuejs.org/v2/guide/state-management.html#Simple-State-Management-from-Scratch
|
|
[one-way-data-flow]: https://vuejs.org/v2/guide/components.html#One-Way-Data-Flow
|
|
[vue-test]: https://vuejs.org/v2/guide/unit-testing.html
|
|
[issue-boards-service]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/assets/javascripts/boards/services/board_service.js.es6
|
|
[flux]: https://facebook.github.io/flux
|
|
[vuex-docs]: https://vuex.vuejs.org
|
|
[vuex-structure]: https://vuex.vuejs.org/en/structure.html
|
|
[vuex-mutations]: https://vuex.vuejs.org/en/mutations.html
|
|
[vuex-testing]: https://vuex.vuejs.org/en/testing.html
|
|
[axios]: https://github.com/axios/axios
|
|
[axios-interceptors]: https://github.com/axios/axios#interceptors
|
|
|