判断App是否首次启动

现在的APP中流行在程序第一次启动时显示一些新手引导页面，下面的代码可用于判断此APP是否第一次启动，或升级后的第一次启动。

#define LAST_RUN_VERSION_KEY        @"last_run_version_of_application"
- (BOOL) isFirstLoad{
     NSString *currentVersion = [[[NSBundle mainBundle] infoDictionary]
         objectForKey:@"CFBundleShortVersionString"];    

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    NSString *lastRunVersion = [defaults objectForKey:LAST_RUN_VERSION_KEY];

    if (!lastRunVersion) {
         [defaults setObject:currentVersion forKey:LAST_RUN_VERSION_KEY];
         return YES;
        // App is being run for first time
    }
    else if (![lastRunVersion isEqualToString:currentVersion]) {
        [defaults setObject:currentVersion forKey:LAST_RUN_VERSION_KEY];
        return YES;
        // App has been updated since last run
    }
    return NO;
}

参考：
Check for first use
app 新手引导设计
Top 6 Help Design Patterns for iPhone Apps