Swift：将参数添加到协议功能 [英] Swift: Adding parameter to protocol function

问题描述

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.

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