ios - 如何引用非转义闭包？

Question

我有以下代码

class Child {
    var onClosureFromParent: ((Int) -> Void)?

    // Ok.
    func setupEscaping(onClosureFromParent: @escaping (Int) -> Void) {
        self.onClosureFromParent = onClosureFromParent
    }

    // Error: Assigning non-escaping parameter 'onClosureFromParent' to an @escaping closure
    func setupNonEscaping(onClosureFromParent: (Int) -> Void) {

        // FIXME:
        self.onClosureFromParent = onClosureFromParent
    }
}

我想知道，我怎样才能引用非转义闭包？

Answer 1

来自官方文档:

A closure is said to escape a function when the closure is passed as an argument to the function, but is called after the function returns. When you declare a function that takes a closure as one of its parameters, you can write @escaping before the parameter’s type to indicate that the closure is allowed to escape.

由于函数中的闭包参数，您正在保存它的引用而不是执行它，这意味着该闭包不会在函数范围内执行。因此，您应该让它逃脱。

func setupNonEscaping(onClosureFromParent: (Int) -> Void) {

       // Saving the reference, not executing it.
       // ie, It will be executed later on...
        self.onClosureFromParent = onClosureFromParent

    }

代码中的某处...

// The closure is executed later on, thus it should outlive the function lifescope.

let param = 10
 self.onClosureFromParent(param)