[swift-evolution] Proposal: Add @requires_super attribute

[Marc Knaup]

+1 always had such issues with UIViewController's lifecycle methods.

But edge cases need to be considered like "throws" for example.
Do I need to call super before I throw something?

On Wed, Dec 16, 2015 at 5:41 PM, Matthew Johnson via swift-evolution <
swift-evolution at swift.org> wrote:

> +1 to this.  Anything that helps ensure inheritance is thought through
> carefully and used correctly is a win.
>
> On Dec 16, 2015, at 10:32 AM, Vester Gottfried via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Some class based libraries/frameworks expect the consumer to subclass
> certain classes and override specific method and require that the super
> implementation of an overridden method is being called.
>
> Not calling the super implementation is a common source of bugs that may
> be prevented if the compiler checks if super is called, like it does in
> some cases of init().
>
> Example:
>
> class Box {
>    @requires_super
>     func addStuff() { ... }
> }
>
> Overriding class Box's addStuff without calling super.addStuff() should
> result in an error
>
> class Chest : Box {
>     override addStuff() {
>          // ERROR: addStuff() requires call to super.addStuff()
>         ...
>     }
> }
>
> Objective-C developers know this as NS_REQUIRES_SUPER and I think its
> worth thinking about adapting it.
>
> I hope my proposal was clear and thanks for reading,
>
> Gottfried
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