[swift-users] unowned self in closure in a playground

[rintaro ishizaki]

2017-02-22 12:53 GMT+09:00 Ray Fix <rayfix at gmail.com>:

>
> On Feb 21, 2017, at 7:32 PM, rintaro ishizaki <fs.output at gmail.com> wrote:
>
> lifetime guaranteed to be around until the method call completes
>
>
> AFAIK, this is true.
> However, in this case, it's not a method call. The lifetime is only
> guaranteed until getter:increment completes.
>
> Demo().increment(3)
> |--------------| lifetime
>
>
> Thanks!  This is an interesting explanation.
>
> It is curious that naming the variable cases different behavior.
> IOW, this doesn’t have a problem:
>
> let demo = Demo()
> demo.increment(3)
>
> Lifetime seems to last the entire expression.
>
>
I'm not sure, but I think the compiler is just lazy enough to release the "
demo" value *after* the entire expression or scope finishes.
Again, I'm not sure. :)

Anyway, If I were you, I would define a wrapper method:

class Demo {
  var value = 0

  lazy var _increment: (Int) -> Void { [unowned self] by in ... }
  func increment(by: Int) {
    _increment(by)
  }
}
Demo().increment(by: 3)



> Ray
>
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