swift - Variable - didSet and willSet

Question

I understand how to use didSet and willSet for variables but not really why. When should I use these methods and why?

Usually when you update a value you have some kind of button for example where you update a textField and then set a variables value to the textFields for example. If I want to pass something to another viewController or I do it in the button action.

So my question is:
When and why should I use didSet and willSet for my variables?

Answer 1

有时你想观察一个变量的值变化。那是有用didSet的时候。willSet

didSet在值更改后调用，您可以使用它来通知某些 Manager 或执行您需要的任何操作。

willSet有时用于在将值赋予变量之前对其进行修改。例如，您收到String来自服务器的时间戳，您希望将其转换为可读的日期文本。

Answer 2

当您需要观察变量的值变化时，您需要使用变量的 didset/willset。

willSet -- 在存储值之前调用。didSet -- 在存储新值后立即调用。

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