Swift：将参数添加到协议功能

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考虑以下代码，当按下按钮时，该代码将显示正在工作 ：

Consider the following code, which prints "working" when a button is pressed:

protocol MyClassDelegate: class { func foo() } class MyClass { weak var delegate: MyClassDelegate? func foo() { delegate?.foo() } let button: UIButton = { button.addTarget(self, action: #selector(foo), for: .touchUpInside) return button }() } class MyViewController { ... } extension MyViewController: MyClassDelegate { func foo() { print("working") } }

当我尝试向 MyClassDelegate 的 foo 方法，正在工作 停止打印（意味着按钮停止工作？）。即：

When I try adding a parameter to MyClassDelegate's foo method, "working" stops printing (meaning the button stops working?). I.e.:

protocol MyClassDelegate: class { func foo(_ str: String) } class MyClass { weak var delegate: MyClassDelegate? func foo() { delegate?.foo("working") } let button: UIButton = { button.addTarget(self, action: #selector(foo), for: .touchUpInside) return button }() } class MyViewController { ... } extension MyViewController: MyClassDelegate { func foo(_ str: String) { print(str) } }

如何获取带有参数的第二版代码？谢谢。

How can I get the second version of the code with the parameter to work? Thanks.

推荐答案

问题是 button 需要声明使用 lazy var 而不是使用 let 。

The problem was that button needs to be a declared with lazy var rather than with let.