ios - Swift 错误 - 不可变值 '' 可能无法传入

Question

我更新到新的 Swift 1.1。我有一个可选变量:

let bookingButton: GreenButton?

当我尝试将此 UIView 子类添加为 subview (self 是 UIView)时，出现以下错误:

Immutable value '' may not be passed inout

有什么想法吗？

Answer 1

inout 指定一个可以被函数改变的参数。这里你传递了一个let(一个不可变的参数)所以这是不兼容的。您可以将 lookingButton 从 let 更改为 var 以解决此问题。

如 Apple 文档中所述:

You can only pass a variable as the argument for an in-out parameter. You cannot pass a constant or a literal value as the argument, because constants and literals cannot be modified. You place an ampersand (&) directly before a variable’s name when you pass it as an argument to an inout parameter, to indicate that it can be modified by the function.