解决[User Defaults] Failed to read values in CFPrefsPlistSource

在做iOS Extension时，当你试图向APP Group写入数据，调试时可能会报以下错误：

[User Defaults] Failed to read values in CFPrefsPlistSource<0x1700f8380> (Domain: group.com.company.App, User: kCFPreferencesAnyUser, ByHost: Yes, Container: (null)): Using kCFPreferencesAnyUser with a container is only allowed for System Containers

出现这个错误，很可能是因为疏忽写下了以下代码：

[[NSUserDefaults standardUserDefaults] initWithSuiteName:@"group.xxx.com"];

因为这个方法重置了你的默认的沙盒。而APP Group的沙盒获取方法为：

[[NSUserDefaults alloc] initWithSuiteName:@"group.xxx.com"];

正是因为standardUserDefaults与alloc的差异导致了上述错误