判断是否是第一次使用app

+ (BOOL)isAppFirstUse {
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    
    if ([userDefaults objectForKey:IS_FIRST_USE] == nil) {
        return YES;
    }
    
    return [[userDefaults objectForKey:IS_FIRST_USE] boolValue];
}

+ (BOOL)saveAppIsFirstUse:(BOOL) isFirstUse {
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    
    [userDefaults setObject:@(isFirstUse) forKey:IS_FIRST_USE];
    [userDefaults synchronize];
    
    return isFirstUse;
}