根据iOS屏幕更改故事板不起作用

Question

我不是XCode 6新约束系统的忠实粉丝，所以我决定为每个iPhone尺寸制作自己的故事板，但它并非100％正常工作。它适用于iPhone 4和iPhone 5，但在iPhone 6或iPhone 6+上进行测试时，它会显示iPhone 5故事板。

示例：我使用iPhone 4模拟器运行，我在该故事板上的标签上写着＆＃39; 4＆＃39;。

然后我运行了iPhone 5模拟器，我在故事板上的标签上写着＆＃39; 5＆＃39;。

然后，我运行iPhone 6和6+模拟器，它显示与iPhone 5故事板相同的标签（它显示错误的故事板）

我想知道你们是否可以指出我的错误，我很感激！

以下是我的故事板：

这是我的代码（在我的appdelegate.m文件中）

 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

CGSize iOSScreenSize = [[UIScreen mainScreen] bounds].size;

if (iOSScreenSize.height == 480)
{
    // iPhone 4/4S
    UIStoryboard *iPhone4 = [UIStoryboard storyboardWithName:@"iPhone4" bundle:nil];

    UIViewController *initialViewController = [iPhone4 instantiateInitialViewController];

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    self.window.rootViewController = initialViewController;

    [self.window makeKeyAndVisible];
}

if (iOSScreenSize.height == 568)
{
    // iPhone 5/5S
    UIStoryboard *iPhone5 = [UIStoryboard storyboardWithName:@"iPhone5" bundle:nil];

    UIViewController *initialViewController = [iPhone5 instantiateInitialViewController];

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    self.window.rootViewController = initialViewController;

    [self.window makeKeyAndVisible];
}

if (iOSScreenSize.height == 667)
{
    // iPhone 6
    UIStoryboard *iPhone6 = [UIStoryboard storyboardWithName:@"iPhone6" bundle:nil];

    UIViewController *initialViewController = [iPhone6 instantiateInitialViewController];

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    self.window.rootViewController = initialViewController;

    [self.window makeKeyAndVisible];
}
if (iOSScreenSize.height == 736)
{
    // iPhone 6+
    UIStoryboard *iPhone6Plus = [UIStoryboard storyboardWithName:@"iPhone6+" bundle:nil];

    UIViewController *initialViewController = [iPhone6Plus instantiateInitialViewController];

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    self.window.rootViewController = initialViewController;

    [self.window makeKeyAndVisible];
}

    return YES;
}