swiftautomatic-ref-countinggrand-central-dispatch

Should I use `weak self` on a custom stored queue?

I know that we can use strong self in DispatchQueues when we call it directly in the code, for example:

func foo() {
    DispatchQueue.global().async {
        print(self.someProperty)
    }
}

But what about my custom queue, if I keep it in the class? Should I use weak self or it works the same and there is no need to worry about leaks?

class MyClass {
    
    let queue = DispatchQueue(
        label: "MyQueue",
        qos: .userInitiated
    )
    
    func foo() {
        queue.async { [weak self] in
            guard let self else { return }
            print(self.someProperty)
        }
    }
}

In this case my custom queue is stored in a class variable and probably I should use weak self. Or not?

Solution

  • queue.async closure does retain self without [weak self]. However, it's temporary, it will disappear immediately when dequeued. So there is no retain cycle here.

    AFAIK, it's more like data flow than a retain cycle.