> On 6. Oct 2017, at 14:49, Spencer Kohan via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> Hi all,
>
> In migrating to swift 4 I've noticed one thing which has changed is there is
> no longer support for the automatic re-initialization of lazy variables.
>
> In swift 3 I could declare a variable like this:
>
> lazy var myVar : MyType! = {
> return makeMyVar()
> }()
>
> And then if I wanted that initialization block to be executed again, I could
> just nullify the variable:
>
> self.myVar = nil
>
> It looks as if this was never intentional, and according to this bug report
> <https://bugs.swift.org/browse/SR-5172>, and now the nullified variable stay
> null rather than executing the initialization block a second time.
>
> Has the possibility been discussed of providing a way to force lazy vars to
> initialize more than once? Working with swift 3 I found this behavior to be
> very useful in some use cases. For example in computer graphics it's a nice
> way to handle the generation of assets which only need to be created in the
> case of some relatively infrequent event, like for instance a window resize.
> It seems I'm not alone - the top stack-overflow question
> <https://stackoverflow.com/questions/25072597/re-initialize-a-lazy-initialized-variable-in-swift>
> related to re-initializing lazy variables has over 10k views, so I suppose
> others have found a use case for this functionality as well.
>
> Cheers,
> Spencer Kohan
> _______________________________________________
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> swift-evolution@swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
Yes, the issue has come up before. There is/was a plan to generalise “lazy” as
some kind of “property behaviour” which could support more advanced
functionality, such as you described. AFAIK it doesn’t have a specific place on
the roadmap.
See:
https://github.com/apple/swift/blob/master/test/Prototypes/property_behaviors/lazy.swift
<https://github.com/apple/swift/blob/master/test/Prototypes/property_behaviors/lazy.swift>
- Karl
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