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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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Swift:将参数添加到协议功能
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