如果我不使用classForCoder，iOS Swift的Facebook登录按钮将不会显示

Question

我正在尝试将Facebook单点登录集成到我的iOS应用程序之一。 我遵循了Facebook的指示，当我尝试运行该应用程序时，出现以下错误

Unknown class FBSDKLoginButton in Interface Builder file.

在网上搜索后，我发现添加以下代码可以解决该问题。

FBSDKLoginButton.classForCoder()

我的问题是，此代码的重要意义是什么？ 这在后台执行什么操作？

Answer 1

从苹果的基金会框架参考 ：

classForCoder是Overridden by subclasses to substitute a class other than its own during coding. (read-only) Overridden by subclasses to substitute a class other than its own during coding. (read-only)

This method is invoked by NSCoder. NSObject's implementation returns the receiver's class. The private subclasses of a class cluster substitute the name of their public superclass when being archived.

声明书 ：

var classForCoder: AnyClass { get }