几乎是 Marc 和 Chris 所说的，但我更喜欢在应用程序退出时更改该值，以防应用程序的多个区域需要知道关于它.在代码中:

Pretty much what Marc and Chris said, though I prefer to change the value when the app quits in case there're multiple areas of the application that need to know about it. In code:

目标 C

// -applicationDidFinishLaunching:
[[NSUserDefaults standardUserDefaults] registerDefaults:[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],@"firstLaunch",nil]];
// to check it:
[[NSUserDefaults standardUserDefaults] boolForKey:@"firstLaunch"];
// -applicationWillTerminate:
[[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"firstLaunch"];

Swift 5.0

// -applicationDidFinishLaunching:
UserDefaults.standard.register(defaults: ["firstLaunch":true])
// to check it:
UserDefaults.standard.bool(forKey: "firstLaunch")
// -applicationWillTerminate:
UserDefaults.standard.set(false, forKey: "firstLaunch")