Do capture lists of inner closures need to redeclare `self` as `weak` or `unowned`?

Question

If I have a closure passed to a function like this:

 someFunctionWithTrailingClosure { [weak self] in
     anotherFunctionWithTrailingClosure { [weak self] i         


        

Answer 1

Updated for Swift 4.2:

public class CaptureListExperiment {

    public init() {

    }

    func someFunctionWithTrailingClosure(closure: @escaping () -> ()) {
        print("starting someFunctionWithTrailingClosure")

        DispatchQueue.global().asyncAfter(deadline: .now() + 1) {
            closure()
            print("finishing someFunctionWithTrailingClosure")
        }
    }

    func anotherFunctionWithTrailingClosure(closure: @escaping () -> ()) {
        print("starting anotherFunctionWithTrailingClosure")

        DispatchQueue.global().asyncAfter(deadline: .now() + 1) {
            closure()
            print("finishing anotherFunctionWithTrailingClosure")
        }
    }

    func doSomething() {
        print("doSomething")
    }

    public func testCompletionHandlers() {
        someFunctionWithTrailingClosure { [weak self] in
            guard let self = self else { return }
            self.anotherFunctionWithTrailingClosure { // [weak self] in
                self.doSomething()
            }
        }
    }

    // go ahead and add `deinit`, so I can see when this is deallocated

    deinit {
        print("deinit")
    }
}

try it Playgorund:

func performExperiment() {

    let obj = CaptureListExperiment()

    obj.testCompletionHandlers()
    Thread.sleep(forTimeInterval: 1.3)
}

performExperiment()