On Apr 27, 2016, at 17:23, Howard Lovatt via swift-evolution
<[email protected]<mailto:[email protected]>> wrote:
I think that you should *always* have to write `override` when implementing a
protocol method, you can think of this as override an abstract declaration. In
particular I think the following should be enforced:
protocol A { func a() }
extension A { override func a() { ... } }
struct AnA: A { override func a() { ... } }
protocol B { func b() }
struct AB: B { override func b() { ... } }
I'm rather new to the list - but I would like to say that I agree with this. I
think it gives clarity both to code readability, and for learning the language.
Best
Josh
I think this change will work out well since it mimics what happened in Java,
originally the Java annotation `@Override` was used much like `override` is
currently used in Swift. However it was problematic and was changed so that you
always add the annotation, as shown above (in the Swift context). One of the
big advantages of this change is that the error messages are much better (this
was very noticeable in Java).
This proposal has come up before on swift-evolution, so it obviously has some
support.
On Thursday, 28 April 2016, Erica Sadun via swift-evolution
<[email protected]<mailto:[email protected]>> wrote:
From the Swift Programming Language: Methods on a subclass that override the
superclass's implementation are marked with override-overriding a method by
accident, without override, is detected by the compiler as an error. The
compiler also detects methods with override that don't actually override any
method in the superclass.
I would like to extend this cautious approach to protocols, forcing the
developer to deliberately override an implementation that's inherited from a
protocol extension. This would prevent accidental overrides and force the user
to proactively choose to implement a version of a protocol member that already
exists in the protocol extension.
I envision this as using the same `override` keyword that's used in class based
inheritance but extend it to protocol inheritance:
protocol A {
func foo()
}
extension A {
func foo() { .. default implementation ... }
}
type B: A {
override required func foo () { ... overrides implementation ... }
}
I'd also like to bring up two related topics, although they probably should at
some point move to their own thread if they have any legs:
Related topic 1: How should a consumer handle a situation where two unrelated
protocols both require the same member and offer different default
implementations. Can they specify which implementation to accept or somehow run
both?
type B: A, C {
override required func foo() { A.foo(); C.foo() }
}
Related topic 2: How can a consumer "inherit" the behavior of the default
implementation (like calling super.foo() in classes) and then extend that
behavior further. This is a bit similar to how the initialization chaining
works. I'd like to be able to call A.foo() and then add custom follow-on
behavior rather than entirely replacing the behavior.
type B: A {
override required func foo() { A.foo(); ... my custom behavior ... }
}
cc'ing in Jordan who suggested a new thread on this and Doug, who has already
expressed some objections so I want him to have the opportunity to bring that
discussion here.
- E
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