Implement unhandled protocol method in extension

Question

I'm trying to implement some push notification methods in my Cordova plugin. Cordova creates their own UIApplicationDelegate, called CDVAppDelegate, so I tried to extend that and use swizzling to add my methods.

However, when I implement an optional protocol method that is unimplemented in CDVAppDelegate, and use swizzling to make it available, this new method isn't called. If I hack the CDVAppDelegate code to implement this method, the new method does get called.

Here are some code snippets - hopefully that will help clarify the situation:

In CDVAppDelegate.h

@interface CDVAppDelegate : NSObject <UIApplicationDelegate>{}

In CDVAppDelegate.m

@implementation CDVAppDelegate

// added by me
- (void)application:(UIApplication *)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken {
    return;
}

In my "extension CDVAppDelegate {...}"

@objc func swizzled_application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
    NSLog("\(TAG) APNs token retrieved: \(deviceToken)")
    self.swizzled_application(application, didRegisterForRemoteNotificationsWithDeviceToken:deviceToken) // swizzled, so this calls original
    ...
}

How can I get this working without modifying CDVAppDelegate.m?

Answer 1

The method class_addMethod lets me implement the unimplemented methods. You can call this and fallback on method_exchangeImplementations if it doesn't work (if the selector already has a method implementation).