Understanding the Problem and Objective

In this article, we will delve into a common problem faced by iOS developers who need to implement custom URL handling for their applications. The goal is to create an application that can seamlessly open URLs both within its own app (using private methods) and use the default system functionality.

We’ll explore the intricacies of how UIApplication handles URLs, understand why overriding the default openURL: method might not be suitable for every situation, and provide a practical solution using subclassing and Info.plist configuration.

Background on UIApplication and URL Handling

When an application is launched or during runtime, iOS presents the user with various options to open links. These include:

1. Opening URLs within the application itself (using UIWebView or other mechanisms).
2. Browsing through Safari.
3. Opening iTunes links directly in iTunes.

By default, iOS uses the UIApplication class to handle these URL opening operations. The openURL: method is used by UIApplication to open URLs based on their scheme (e.g., http, https, telnet).

Private Methods for Custom URL Handling

Developers often create private methods within the AppDelegate or elsewhere in their codebase to override this default behavior and handle specific links within their application. This approach works well when an application requires custom handling for a particular set of URLs.

However, in some cases, users might want to use the default system functionality for opening iTunes links or other types of links not handled by the private method. In such scenarios, using a combination of both methods (private and default) can be challenging.

Solution: Subclassing UIApplication

To achieve flexibility without overriding all the default behaviors, one approach is to subclass UIApplication directly and override the openURL: method within it. This allows us to selectively choose when to use our custom implementation versus relying on the system’s behavior for specific links.

Subclassing UIApplication

## Creating a Subclass of UIApplication
To achieve our goal, we create a new subclass called `ECApplication` (or any other name that suits our needs) and override the `openURL:` method in it.

@implementation ECApplication

- (BOOL)openURL:(NSURL*)url
{
    // Our custom logic for opening URLs within the app goes here
    AppDelegate *MyWatcher = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    
    if (MyWatcher.currentViewController)
    {
        [MyWatcher.currentViewController handleURL:url];
        return YES;
    }
    return NO;
}

@end

Modifying Info.plist

To make our custom subclass the “principle class” for handling URLs, we need to update the Info.plist file with the new subclass. The process involves changing the value of the “Principal Class” key from the default UIApplication to our newly created subclass.

For instance, if we’re using Xcode 11 or later, the process might look like this:

1. Open your project in Xcode.
2. In the Product menu, select Edit Scheme…
3. Navigate to the Editor Info tab on the left.
4. Under Build settings, locate the Principal Class setting and update its value from UIApplication to our subclass name (ECApplication).

Conclusion

Subclassing UIApplication provides a direct way to override or selectively use the default behavior for opening URLs within your app. This approach allows you to maintain control over custom URL handling while still leveraging the system’s functionality for other types of links.

By understanding how iOS handles URLs and implementing a solution that seamlessly integrates private methods with the default system behavior, developers can create robust applications that cater to diverse user needs and preferences.

Last modified on 2025-02-19