Updating closures to Swift 3 - @escaping

Question

I\'ve updated my code to Xcode 8.0 beta 6 but I got stuck with what seems to be about the new non escaping closure default. In the following code Xcode suggests to add

Answer 1

@noescape

From xcode 8 beta 6 @noescape is the default. Prior to that, @escaping was the default. Anybody updating to swift 3.0 from previous versions might face this error.

You can not store a @noescape closure inside a variable. Because if you can store a closure inside a variable, you can execute the closure from anywhere in your code. But @noescape states that the closure parameter can not escape the body of the function.

This will give compiler error in Xcode 8

class MyClass {

    var myClosure: (() -> ())?

    func doSomething(finishBlock: () -> ()) {
        myClosure = finishBlock    // ‼️ Error: Assigning non-escaping parameter 'finishBlock' to an @escaping closure
    }
}

This will compile ok (explicitly write @escaping)

class MyClass {

    var myClosure: (() -> ())?

    func doSomething(finishBlock: @escaping () -> ()) {
        myClosure = finishBlock
    }
}

Benefits of @noescape:

• Compiler can optimize your code for better Performance
• Compiler can take care of memory management
• There is no need to use a weak reference to self in the closure

For details check out: Make non-escaping closures the default