> On Sep 13, 2017, at 18:59 , Jon Shier <[email protected]> wrote:
>
> I think there’s something strange with popFirst. It doesn’t show up in
> the autocomplete in Xcode, but it compiles, and popLast doesn’t throw the
> same error. removeFirst doesn’t either, though it’s unsafe. Weird.
extension
Array
{
public
mutating
func
popFirst()
-> Array.Element?
{
if self.count > 0
{
return self.removeFirst()
}
return nil
}
}
>
>
>
> Jon
>
>
>> On Sep 13, 2017, at 9:47 PM, Zhao Xin via swift-users
>> <[email protected]> wrote:
>>
>> I begin to think it is related to how you `popFirst()` implemented. Check it
>> or post it here.
>>
>> Zhao Xin
>>
>> On Thu, Sep 14, 2017 at 9:36 AM, Roderick Mann <[email protected]> wrote:
>> Yeah, that's not it. I made the change you suggested, I get the same error.
>>
>> > On Sep 13, 2017, at 18:11 , Zhao Xin <[email protected]> wrote:
>> >
>> > Change `self` to `ModelFetcher`. You are calling a class static property,
>> > not a class instance property.
>> >
>> > Zhao Xin
>> >
>> > On Thu, Sep 14, 2017 at 8:37 AM, Rick Mann via swift-users
>> > <[email protected]> wrote:
>> > Moving to Swift 4, I'm running into an issue for which I can't seem to
>> > find an answer in google:
>> >
>> > "Cannot use mutating member on immutable value: 'self' is immutable"
>> >
>> > The code looks like:
>> >
>> > class
>> > ModelFetcher : NSObject, URLSessionDelegate
>> > {
>> > ...
>> > static let managerDispatchQueue =
>> > DispatchQueue(label: "Model Download Manager Queue")
>> > static var pendingFetchers =
>> > [ModelFetcher]()
>> > static var currentFetcher: ModelFetcher?
>> >
>> > class
>> > func
>> > startNextFetcher()
>> > {
>> > self.managerDispatchQueue.async
>> > {
>> > guard
>> > self.currentFetcher == nil,
>> > let mf = self.pendingFetchers.popFirst()
>> > ~~~~ ^ error: cannot
>> > use mutating member on immutable value: 'self' is immutable
>> > else
>> > {
>> > return
>> > }
>> >
>> > self.currentFetcher = mf
>> > mf.start()
>> > }
>> > }
>> > ...
>> > }
>> >
>> > This code compiled fine in Xcode 8, or in Xcode 9/Swift 3.2 as a
>> > monolithic app (the error shows up when this code is factored into a
>> > framework). Other mutating references to self seem to compile okay (e.g.
>> > "self.currentFetcher = nil" or "self.pendingFetchers.remove(at: idx)").
>> > Not sure what's special about this one.
>> >
>> >
>> > --
>> > Rick Mann
>> > [email protected]
>> >
>> >
>> > _______________________________________________
>> > swift-users mailing list
>> > [email protected]
>> > https://lists.swift.org/mailman/listinfo/swift-users
>> >
>>
>>
>> --
>> Rick Mann
>> [email protected]
>>
>>
>>
>> _______________________________________________
>> swift-users mailing list
>> [email protected]
>> https://lists.swift.org/mailman/listinfo/swift-users
>
--
Rick Mann
[email protected]
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