如果我不使用classForCoder，iOS Swift的Facebook登錄按鈕將不會顯示

Question

我正在嘗試將Facebook單點登錄集成到我的iOS應用程序之一。 我遵循了Facebook的指示，當我嘗試運行該應用程序時，出現以下錯誤

Unknown class FBSDKLoginButton in Interface Builder file.

在網上搜索后，我發現添加以下代碼可以解決該問題。

FBSDKLoginButton.classForCoder()

我的問題是，此代碼的重要意義是什么？ 這在后台執行什么操作？

Answer 1

從蘋果的基金會框架參考 ：

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.

聲明書 ：

var classForCoder: AnyClass { get }