[swift-evolution] Proposal: partial initialization before returning nil from an initializer
Félix Cloutier
felixcca at yahoo.ca
Thu Dec 17 10:23:04 CST 2015
Oh, sweet.
Is there a changelog anywhere? I really like LLVM's release notes and how they're updated during development.
Félix
> Le 17 déc. 2015 à 11:20:08, Keith Smiley <keithbsmiley at gmail.com> a écrit :
>
> I believe this has already been fixed here: https://github.com/apple/swift/commit/f524802e129f17de16fa6f8c3f08e5bcf75cc581 <https://github.com/apple/swift/commit/f524802e129f17de16fa6f8c3f08e5bcf75cc581>
> On Thu, Dec 17, 2015 at 10:01 Félix Cloutier <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> Hi all,
>
> Initializers can now fail, but objects still need to be fully initialized before you can return `nil` from them. For instance:
>
> class Foo {
> let bar: Int
> init?(baz: Int) {
> guard baz < 100 else {
> return nil
> }
> self.bar = baz
> }
> }
>
> This trivial example causes the following error: "all stored properties of a class instance must be initialized before returning nil from an initializer".
>
> For integers, that's easy: you can simply set them to zero. However, sometimes, you'd want initialization to fail because the arguments you received don't allow you to properly initialize a member. In these cases, you have to make the fields Optionals (implicitly unwrapped or not) to overcome this.
>
> I remember that Chris said that this is a temporary issue and that it would eventually be fixed. I'm starting this thread because I'd love to have this with or before Swift 3 and I'd like to see who thinks this is big enough of an issue to rival the proposals we already have.
>
> Félix
>
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