Rewrote self-type tour #748
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hey I know I've done a lot of reviewing of these so it's logical to request me as a reviewer, but actually, can we spread it around more? I don't want to be in the position where it's always me. you can ask other members of the Scala team at Lightbend, Scala Center folks, etc. |
| previous-page: compound-types | ||
| prerequisite-knowledge: nested-classes, mixin-class-composition | ||
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| When writing extensible code, it can be useful to declare a self-type as a means of dependency injection. |
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Not to minimize the difficulty, but this is quite opaque. Maybe something like: Self-types are a way to declare that a trait must be mixed into another trait, even though it doesn't directly extend it. That makes the members of the dependency available without imports.
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| When writing extensible code, it can be useful to declare a self-type as a means of dependency injection. | ||
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| To use a self-type in a trait, write an identifier, the type of another trait to mix in, and a right fat arrow (e.g. `someIdentifier: SomeOtherTrait =>`). |
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The syntax is actually weird. Maybe be up-front about it. A self-type is a way to narrow the type of thisor another identifier that aliasesthis. The syntax looks like normal function syntax but means something entirely different. Darn, just noticed I introduced extra backticks.
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| Because we said `this: User =>` in `trait Tweeter`, now the variable `username` is in scope for the `tweet` method. This also means that since `VerifiedTweeter` extends `Tweeter`, it must also mix-in `User` (using `with User`). | ||
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| Whenever a trait needs to mix-in another trait, a self-type can be used to bring the other trait's members into scope. |
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Yes, this could be said up front.
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@SethTisue you could put me on the reviewer list as "stuff Seth is sick of reviewing." |
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@SethTisue sure, no problem. I'll try to ping the Gitter channel again. |
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