375 lines
11 KiB
Markdown
375 lines
11 KiB
Markdown
# Vuex
|
|
To manage the state of an application you should use [Vuex][vuex-docs].
|
|
|
|
_Note:_ All of the below is explained in more detail in the official [Vuex documentation][vuex-docs].
|
|
|
|
## Separation of concerns
|
|
Vuex is composed of State, Getters, Mutations, Actions and Modules.
|
|
|
|
When a user clicks on an action, we need to `dispatch` it. This action will `commit` a mutation that will change the state.
|
|
_Note:_ The action itself will not update the state, only a mutation should update the state.
|
|
|
|
## File structure
|
|
When using Vuex at GitLab, separate this concerns into different files to improve readability:
|
|
|
|
```
|
|
└── store
|
|
├── index.js # where we assemble modules and export the store
|
|
├── actions.js # actions
|
|
├── mutations.js # mutations
|
|
├── getters.js # getters
|
|
├── state.js # state
|
|
└── mutation_types.js # mutation types
|
|
```
|
|
The following example shows an application that lists and adds users to the state.
|
|
(For a more complex example implementation take a look at the security applications store in [here](https://gitlab.com/gitlab-org/gitlab-ee/tree/master/ee/app/assets/javascripts/vue_shared/security_reports/store))
|
|
|
|
### `index.js`
|
|
This is the entry point for our store. You can use the following as a guide:
|
|
|
|
```javascript
|
|
import Vue from 'vue';
|
|
import Vuex from 'vuex';
|
|
import * as actions from './actions';
|
|
import * as getters from './getters';
|
|
import mutations from './mutations';
|
|
import state from './state';
|
|
|
|
Vue.use(Vuex);
|
|
|
|
export const createStore = () => new Vuex.Store({
|
|
actions,
|
|
getters,
|
|
mutations,
|
|
state,
|
|
});
|
|
export default createStore();
|
|
```
|
|
|
|
### `state.js`
|
|
The first thing you should do before writing any code is to design the state.
|
|
|
|
Often we need to provide data from haml to our Vue application. Let's store it in the state for better access.
|
|
|
|
```javascript
|
|
export default {
|
|
endpoint: null,
|
|
|
|
isLoading: false,
|
|
error: null,
|
|
|
|
isAddingUser: false,
|
|
errorAddingUser: false,
|
|
|
|
users: [],
|
|
};
|
|
```
|
|
|
|
#### Access `state` properties
|
|
You can use `mapState` to access state properties in the components.
|
|
|
|
### `actions.js`
|
|
An action is a payload of information to send data from our application to our store.
|
|
|
|
An action is usually composed by a `type` and a `payload` and they describe what happened.
|
|
Enforcing that every change is described as an action lets us have a clear understanding of what is going on in the app.
|
|
|
|
In this file, we will write the actions that will call the respective mutations:
|
|
|
|
```javascript
|
|
import * as types from './mutation_types';
|
|
import axios from '~/lib/utils/axios_utils';
|
|
import createFlash from '~/flash';
|
|
|
|
export const requestUsers = ({ commit }) => commit(types.REQUEST_USERS);
|
|
export const receiveUsersSuccess = ({ commit }, data) => commit(types.RECEIVE_USERS_SUCCESS, data);
|
|
export const receiveUsersError = ({ commit }, error) => commit(types.REQUEST_USERS_ERROR, error);
|
|
|
|
export const fetchUsers = ({ state, dispatch }) => {
|
|
dispatch('requestUsers');
|
|
|
|
axios.get(state.endpoint)
|
|
.then(({ data }) => dispatch('receiveUsersSuccess', data))
|
|
.catch((error) => {
|
|
dispatch('receiveUsersError', error)
|
|
createFlash('There was an error')
|
|
});
|
|
}
|
|
|
|
export const requestAddUser = ({ commit }) => commit(types.REQUEST_ADD_USER);
|
|
export const receiveAddUserSuccess = ({ commit }, data) => commit(types.RECEIVE_ADD_USER_SUCCESS, data);
|
|
export const receiveAddUserError = ({ commit }, error) => commit(types.REQUEST_ADD_USER_ERROR, error);
|
|
|
|
export const addUser = ({ state, dispatch }, user) => {
|
|
dispatch('requestAddUser');
|
|
|
|
axios.post(state.endpoint, user)
|
|
.then(({ data }) => dispatch('receiveAddUserSuccess', data))
|
|
.catch((error) => dispatch('receiveAddUserError', error));
|
|
}
|
|
```
|
|
|
|
#### Actions Pattern: `request` and `receive` namespaces
|
|
When a request is made we often want to show a loading state to the user.
|
|
|
|
Instead of creating an action to toggle the loading state and dispatch it in the component,
|
|
create:
|
|
1. An action `requestSomething`, to toggle the loading state
|
|
1. An action `receiveSomethingSuccess`, to handle the success callback
|
|
1. An action `receiveSomethingError`, to handle the error callback
|
|
1. An action `fetchSomething` to make the request.
|
|
1. In case your application does more than a `GET` request you can use these as examples:
|
|
1. `PUT`: `createSomething`
|
|
2. `POST`: `updateSomething`
|
|
3. `DELETE`: `deleteSomething`
|
|
|
|
The component MUST only dispatch the `fetchNamespace` action. Actions namespaced with `request` or `receive` should not be called from the component
|
|
The `fetch` action will be responsible to dispatch `requestNamespace`, `receiveNamespaceSuccess` and `receiveNamespaceError`
|
|
|
|
By following this pattern we guarantee:
|
|
1. All applications follow the same pattern, making it easier for anyone to maintain the code
|
|
1. All data in the application follows the same lifecycle pattern
|
|
1. Actions are contained and human friendly
|
|
1. Unit tests are easier
|
|
1. Actions are simple and straightforward
|
|
|
|
#### Dispatching actions
|
|
To dispatch an action from a component, use the `mapActions` helper:
|
|
```javascript
|
|
import { mapActions } from 'vuex';
|
|
|
|
{
|
|
methods: {
|
|
...mapActions([
|
|
'addUser',
|
|
]),
|
|
onClickUser(user) {
|
|
this.addUser(user);
|
|
},
|
|
},
|
|
};
|
|
```
|
|
|
|
### `mutations.js`
|
|
The mutations specify how the application state changes in response to actions sent to the store.
|
|
The only way to change state in a Vuex store should be by committing a mutation.
|
|
|
|
**It's a good idea to think of the state before writing any code.**
|
|
|
|
Remember that actions only describe that something happened, they don't describe how the application state changes.
|
|
|
|
**Never commit a mutation directly from a component**
|
|
|
|
```javascript
|
|
import * as types from './mutation_types';
|
|
|
|
export default {
|
|
[types.REQUEST_USERS](state) {
|
|
state.isLoading = true;
|
|
},
|
|
[types.RECEIVE_USERS_SUCCESS](state, data) {
|
|
// Do any needed data transformation to the received payload here
|
|
state.users = data;
|
|
state.isLoading = false;
|
|
},
|
|
[types.REQUEST_USERS_ERROR](state, error) {
|
|
state.isLoading = false;
|
|
},
|
|
[types.REQUEST_ADD_USER](state, user) {
|
|
state.isAddingUser = true;
|
|
},
|
|
[types.RECEIVE_ADD_USER_SUCCESS](state, user) {
|
|
state.isAddingUser = false;
|
|
state.users.push(user);
|
|
},
|
|
[types.REQUEST_ADD_USER_ERROR](state, error) {
|
|
state.isAddingUser = true;
|
|
state.errorAddingUser = error;
|
|
},
|
|
};
|
|
```
|
|
|
|
### `getters.js`
|
|
Sometimes we may need to get derived state based on store state, like filtering for a specific prop.
|
|
Using a getter will also cache the result based on dependencies due to [how computed props work](https://vuejs.org/v2/guide/computed.html#Computed-Caching-vs-Methods)
|
|
This can be done through the `getters`:
|
|
|
|
```javascript
|
|
// get all the users with pets
|
|
export const getUsersWithPets = (state, getters) => {
|
|
return state.users.filter(user => user.pet !== undefined);
|
|
};
|
|
```
|
|
|
|
To access a getter from a component, use the `mapGetters` helper:
|
|
```javascript
|
|
import { mapGetters } from 'vuex';
|
|
|
|
{
|
|
computed: {
|
|
...mapGetters([
|
|
'getUsersWithPets',
|
|
]),
|
|
},
|
|
};
|
|
```
|
|
|
|
### `mutation_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,
|
|
...
|
|
};
|
|
```
|
|
|
|
### Communicating with the Store
|
|
```javascript
|
|
<script>
|
|
import { mapActions, mapState, mapGetters } from 'vuex';
|
|
import store from './store';
|
|
|
|
export default {
|
|
store,
|
|
computed: {
|
|
...mapGetters([
|
|
'getUsersWithPets'
|
|
]),
|
|
...mapState([
|
|
'isLoading',
|
|
'users',
|
|
'error',
|
|
]),
|
|
},
|
|
methods: {
|
|
...mapActions([
|
|
'fetchUsers',
|
|
'addUser',
|
|
]),
|
|
|
|
onClickAddUser(data) {
|
|
this.addUser(data);
|
|
}
|
|
},
|
|
|
|
created() {
|
|
this.fetchUsers()
|
|
}
|
|
}
|
|
</script>
|
|
<template>
|
|
<ul>
|
|
<li v-if="isLoading">
|
|
Loading...
|
|
</li>
|
|
<li v-else-if="error">
|
|
{{ error }}
|
|
</li>
|
|
<template v-else>
|
|
<li
|
|
v-for="user in users"
|
|
:key="user.id"
|
|
>
|
|
{{ user }}
|
|
</li>
|
|
</template>
|
|
</ul>
|
|
</template>
|
|
```
|
|
|
|
### Vuex Gotchas
|
|
|
|
1. Do not call a mutation directly. Always use an action to commit a mutation. Doing so will keep consistency throughout 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. 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 { createStore } from './store';
|
|
import component from './component.vue'
|
|
|
|
describe('component', () => {
|
|
let store;
|
|
let vm;
|
|
let Component;
|
|
|
|
beforeEach(() => {
|
|
Component = Vue.extend(issueActions);
|
|
});
|
|
|
|
afterEach(() => {
|
|
vm.$destroy();
|
|
});
|
|
|
|
it('should show a user', () => {
|
|
const user = {
|
|
name: 'Foo',
|
|
age: '30',
|
|
};
|
|
|
|
store = createStore();
|
|
|
|
// populate the store
|
|
store.dispatch('addUser', user);
|
|
|
|
vm = new Component({
|
|
store,
|
|
propsData: props,
|
|
}).$mount();
|
|
});
|
|
});
|
|
```
|
|
|
|
#### Testing Vuex actions and getters
|
|
Because we're currently using [`babel-plugin-rewire`](https://github.com/speedskater/babel-plugin-rewire), you may encounter the following error when testing your Vuex actions and getters:
|
|
`[vuex] actions should be function or object with "handler" function`
|
|
|
|
To prevent this error from happening, you need to export an empty function as `default`:
|
|
```
|
|
// getters.js or actions.js
|
|
|
|
// prevent babel-plugin-rewire from generating an invalid default during karma tests
|
|
export default () => {};
|
|
```
|
|
|
|
[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
|