Swift:实例方法作为闭包不起作用

Question

var closureA: (String)->()

class Test {
    func instanceMethod(string: String) {
    }
}

let a = Test()

closureA = Test.instanceMethod(a)

closureA("hello")

Xcode10 Playground 显示错误:

错误:无法将“(String) -> ()”类型的值分配给“(String) -> ()”类型闭包A = Test.instanceMethod(a)

我已经读过:https://oleb.net/blog/2014/07/swift-instance-methods-curried-functions/

Answer 1

我认为你错过了闭包的要点，你不能将函数存储在闭包中，但你可以将调用函数的代码与传递到闭包中的变量和函数一起存储仍然需要一个类实例来调用它，所以它应该是这样的:

var closureA: ((String)->())?

class Test {
    func instanceMethod(string: String) {
        print(string)
    }
}

let a = Test()

//Assume you have a variable `str: String` before hand that will execute the code inside closure
closureA = { str in
    a.instanceMethod(string: str)
}

//Actual call to the closure to execute it
closureA?("hello")