[swift-users] Swift 4 "Cannot use mutating member on immutable value: 'self' is immutable"

[Zhao Xin]

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 <rmann at latencyzero.com>
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 <owenzx at gmail.com> 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 <
> swift-users at swift.org> 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
> > rmann at latencyzero.com
> >
> >
> > _______________________________________________
> > swift-users mailing list
> > swift-users at swift.org
> > https://lists.swift.org/mailman/listinfo/swift-users
> >
>
>
> --
> Rick Mann
> rmann at latencyzero.com
>
>
>
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