判断程序首次启动

chenyongyong:不保证正确，但我是这样做的，应该可以

判断程序是否第一次启动：（想着把版本号也注入到KEY值中，不然程序升级后 NSUserDefaults 里的值仍然存在 ）

#define   KeyFirstLaunch             @"keyfirstlaunch"       //是否启动引导

#define   KeyEverLaunch              @"keyeverlaunch"        //已启动过引导

NSString *everLaunch = [NSString stringWithFormat:@"%@-%@",KeyEverLaunch,[[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"]];

    NSString *firstLaunch = [NSString stringWithFormat:@"%@-%@",KeyFirstLaunch,[[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"]];

    if (![[NSUserDefaults standardUserDefaults] boolForKey:everLaunch]) {

        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:everLaunch];

        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:firstLaunch];

        [[NSUserDefaults standardUserDefaults] synchronize];

    } else {

        [[NSUserDefaults standardUserDefaults] setBool:NO forKey:firstLaunch];

        [[NSUserDefaults standardUserDefaults] synchronize];

    }