> On Oct 5, 2016, at 10:07 PM, Cao Jiannan <[email protected]> wrote:
>
> so if developer want to capture an variable inference, must declare a new
> variable.
I don’t follow what you mean here.
>
> class A {
> var value = 1
>
> func test() -> () -> Int {
> var capturedValue = self.value
> let editInfo = { () -> Int in
> capturedValue += 1
> return capturedValue
> }
> return editInfo
> }
> }
>
> let a = A()
>
> let editInfo = a.test()
> print(editInfo()) // 2
> print(a.value) // 1
> print(editInfo()) // 3
> print(a.value) // 1
>
> what about:
>
> class A {
> var value = 1
>
> func test() -> () -> Int {
> let editInfo = { [inout value] () -> Int in
> capturedValue += 1
> return capturedValue
> }
> return editInfo
> }
> }
>
> let a = A()
>
> let editInfo = a.test()
> print(editInfo()) // 2
> print(a.value) // 2
> print(editInfo()) // 3
> print(a.value) // 3
I’m not quite sure what you’re getting at, but this prints what you’re
expecting in the output you have in the comments:
class A {
var value = 1
func test() -> () -> Int {
let editInfo = { () -> Int in
self.value += 1
return self.value
}
return editInfo
}
}
let a = A()
let editInfo = a.test()
print(editInfo()) // 2
print(a.value) // 2
print(editInfo()) // 3
print(a.value) // 3
Mark
>
> > > On Oct 5, 2016, at 9:06 PM, Cao Jiannan via
> > > swift-evolution<[email protected]
> > > <mailto:[email protected]>>wrote:
> > >
> > > for example:
> > >
> > > var a = 1
> > >
> > > let block = { [inout a] in
> > > a += 1
> > > }
> > >
> > > block()
> > > block()
> > >
> > > print(a) // 3
> > This is already how captures work by default in closures and nested
> > functions in Swift:
> >
> > var a = 1
> >
> > let block = { a += 1 }
> >
> > block()
> > block()
> >
> > print(a) // prints 3
> >
> >
> > If you want to capture something immutably you can put it in the capture
> > list:
> >
> > var a = 1
> > let block = { [a] in a += 1 } // error: left side of mutating operator
> > isn't mutable: 'a' is a 'let' constant
> >
> > Mark
> >
> > >
> > >
> > > _______________________________________________
> > > swift-evolution mailing list
> > > [email protected] <mailto:[email protected]>
> > > https://lists.swift.org/mailman/listinfo/swift-evolution
> > > <https://lists.swift.org/mailman/listinfo/swift-evolution>
> >
> >
> >
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