138 lines
3.1 KiB
Markdown
138 lines
3.1 KiB
Markdown
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# GitLab utilities
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We developed a number of utilities to ease development.
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## [`MergeHash`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/gitlab/utils/merge_hash.rb)
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* Deep merges an array of hashes:
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``` ruby
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Gitlab::Utils::MergeHash.merge(
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[{ hello: ["world"] },
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{ hello: "Everyone" },
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{ hello: { greetings: ['Bonjour', 'Hello', 'Hallo', 'Dzien dobry'] } },
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"Goodbye", "Hallo"]
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)
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```
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Gives:
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``` ruby
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[
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{
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hello:
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[
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"world",
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"Everyone",
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{ greetings: ['Bonjour', 'Hello', 'Hallo', 'Dzien dobry'] }
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]
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},
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"Goodbye"
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]
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```
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* Extracts all keys and values from a hash into an array:
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``` ruby
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Gitlab::Utils::MergeHash.crush(
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{ hello: "world", this: { crushes: ["an entire", "hash"] } }
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)
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```
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Gives:
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``` ruby
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[:hello, "world", :this, :crushes, "an entire", "hash"]
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```
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## [`Override`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/gitlab/utils/override.rb)
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* This utility could help us check if a particular method would override
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another method or not. It has the same idea of Java's `@Override` annotation
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or Scala's `override` keyword. However we only do this check when
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`ENV['STATIC_VERIFICATION']` is set to avoid production runtime overhead.
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This is useful to check:
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* If we have typos in overriding methods.
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* If we renamed the overridden methods, making original overriding methods
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overrides nothing.
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Here's a simple example:
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``` ruby
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class Base
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def execute
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end
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end
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class Derived < Base
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extend ::Gitlab::Utils::Override
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override :execute # Override check happens here
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def execute
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end
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end
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```
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This also works on modules:
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``` ruby
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module Extension
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extend ::Gitlab::Utils::Override
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override :execute # Modules do not check this immediately
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def execute
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end
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end
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class Derived < Base
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prepend Extension # Override check happens here, not in the module
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end
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```
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## [`StrongMemoize`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/gitlab/utils/strong_memoize.rb)
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* Memoize the value even if it is `nil` or `false`.
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We often do `@value ||= compute`, however this doesn't work well if
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`compute` might eventually give `nil` and we don't want to compute again.
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Instead we could use `defined?` to check if the value is set or not.
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However it's tedious to write such pattern, and `StrongMemoize` would
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help us use such pattern.
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Instead of writing patterns like this:
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``` ruby
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class Find
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def result
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return @result if defined?(@result)
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@result = search
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end
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end
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```
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We could write it like:
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``` ruby
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class Find
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include Gitlab::Utils::StrongMemoize
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def result
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strong_memoize(:result) do
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search
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end
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end
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end
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```
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* Clear memoization
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``` ruby
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class Find
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include Gitlab::Utils::StrongMemoize
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end
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Find.new.clear_memoization(:result)
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```
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