适用于通用（iPhone / iPad）应用的iOS控制器

Question

I am just working on iOS app and I want to make it universal for both iPhones and iPads. This is done and works without any problems:

if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
    self.viewController_iPhone = [[ViewController_iPhone alloc] initWithNibName:@"ViewController_iPhone" bundle:nil];
} else {
    self.viewController_iPad = [[ViewController_iPad alloc] initWithNibName:@"ViewController_iPad" bundle:nil];
}

if (self.viewController_iPhone == nil)
    self.window.rootViewController = self.viewController_iPad;
else
    self.window.rootViewController = self.viewController_iPhone; 

There is a view for each controller (ViewController_iPad.xib, ViewController_iPhone.xib). It doesn't matter which view is loaded in my problem. In a view there is a subview added (UIScrolView). And in this ScrollView there are two views from xib:

NSArray *nibContents = [[NSBundle mainBundle] loadNibNamed:@"SubView1" owner:self options:nil];
UIView *view = [nibContents objectAtIndex:0];
view.frame = CGRectMake(2, 0, scrollView.frame.size.width - 2, scrollView.frame.size.height);
[scrollView addSubview:view];


nibContents = [[NSBundle mainBundle] loadNibNamed:@"SubView2" owner:self options:nil];
view = [nibContents objectAtIndex:0];
view.frame = CGRectMake(scrollView.frame.size.width + 2 , 0, scrollView.frame.size.width - 4, scrollView.frame.size.height);
[scrollView addSubview:view];

(This code is in iPad/iPhone controller). Still everything is OK. But I don't know how to set owners (in IB) of these subviews that are shown in ScrollView. These subviews are in ScrollView which is in a main view so I want to set owners of these subviews as iPad/iPhone controller. But as a owner can be only one class. Can you tell me how to set owners if I have two main controllers and I don't know which one will be loaded in runtime. Thank you.

EDIT: I have another question: I have ViewController_iPhone. It has a View property and this property is assigned to the "root" view in the main view in ViewController_iPhone (.xib). Can I assign this view property also to subview view? Because I got EXC_BAD_ACCESS error if I assign view property of ViewController_iPhone to a "root" view of subview in IB.

Answer 1

Looks like you need to use a class cluster. This will abstract the iPhone/iPad instantiation, so you don't explicitly need to instantiate one of the two. You can read a bit about class clustering in the Apple documentation:

http://developer.apple.com/library/ios/#documentation/general/Conceptual/DevPedia-CocoaCore/ClassCluster.html

It boils down to creating a master view controller which will handle the allocation of iPhone or iPad subclasses based on the current device.

You should override the ViewController alloc class method:

   + (id)alloc {
       NSString *classString = NSStringFromClass([self class]);

       NSString *append = nil;

       if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
           append = @"_iPhone";
       } else {
           append = @"_iPad";
       }

       NSString *subClassString = [classString stringByAppendingString:append];

       id subClass =  NSClassFromString(subClassString);


       id object;

       if (subClass && ![self isKindOfClass:[subClass class]]) {
           object = [subClass alloc];
       } else {
           object = [super alloc];
       }

       return object;
   }

This way you can just allocate the ViewController class and at runtime the correct class definition will be used to instantiate your view controller. This will allow you to use the ViewController class as the owner in IB provided that you create an abstraction of iPhone and iPad interfaces and define it in their super class.