[swift-evolution] Proposal: partial initialization before returning nil from an initializer

[Kevin Wooten]

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utils/buildbot-release-notes.txt


> On Dec 17, 2015, at 9:23 AM, Félix Cloutier via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 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 <mailto: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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> 
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