feat(ios): addDelegateHandler to add App Delegate handlers (#10371)

apps/automated/src/main.ts

@@ -12,6 +12,13 @@ if (Application.ios) {
 	Application.ios.addNotificationObserver(UIApplicationDidFinishLaunchingNotification, (notification: NSNotification) => {
 		console.log('UIApplicationDidFinishLaunchingNotification:', notification);
 	});
+
+	// Make sure we can add multiple handlers for the same event.
+	for (let i = 0; i < 10; i++) {
+		Application.ios.addDelegateHandler('applicationDidBecomeActive', (application: UIApplication) => {
+			console.log('applicationDidBecomeActive', i, application);
+		});
+	}
 }
 
 // Common events for both Android and iOS.

packages/core/application/application.d.ts

@@ -167,6 +167,14 @@ export class iOSApplication extends ApplicationCommon {
 	 */
 	set delegate(value: UIApplicationDelegate | unknown);
 
+	/**
+	 * Adds a delegate handler for the specified delegate method name. This method does not replace an existing handler,
+	 * but rather adds the new handler to the existing chain of handlers.
+	 * @param methodName The name of the delegate method to add a handler for.
+	 * @param handler A function that will be called when the specified delegate method is called.
+	 */
+	addDelegateHandler<T extends keyof UIApplicationDelegate>(methodName: T, handler: (typeof UIApplicationDelegate.prototype)[T]): void;
+
 	/**
 	 * Adds an observer to the default notification center for the specified notification.
 	 * For more information, please visit 'https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSNotificationCenter_Class/#//apple_ref/occ/instm/NSNotificationCenter/addObserver:selector:name:object:'

packages/core/application/application.ios.ts

@@ -74,6 +74,7 @@ class Responder extends UIResponder implements UIApplicationDelegate {
 
 export class iOSApplication extends ApplicationCommon implements IiOSApplication {
 	private _delegate: UIApplicationDelegate;
+	private _delegateHandlers = new Map<string, Array<Function>>();
 	private _window: UIWindow;
 	private _notificationObservers: NotificationObserver[] = [];
 	private _rootView: View;
@@ -255,6 +256,44 @@ export class iOSApplication extends ApplicationCommon implements IiOSApplication
 		}
 	}
 
+	addDelegateHandler<T extends keyof UIApplicationDelegate>(methodName: T, handler: (typeof UIApplicationDelegate.prototype)[T]): void {
+		// safe-guard against invalid handlers
+		if (typeof handler !== 'function') {
+			return;
+		}
+
+		// ensure we have a delegate
+		this.delegate ??= Responder as any;
+
+		const handlers = this._delegateHandlers.get(methodName) ?? [];
+
+		if (!this._delegateHandlers.has(methodName)) {
+			const originalHandler = this.delegate.prototype[methodName];
+
+			if (originalHandler) {
+				// if there is an original handler, we add it to the handlers array to be called first.
+				handlers.push(originalHandler as Function);
+			}
+
+			// replace the original method implementation with one that will call all handlers.
+			this.delegate.prototype[methodName] = function (...args: any[]) {
+				let res: any;
+				for (const handler of handlers) {
+					if (typeof handler !== 'function') {
+						continue;
+					}
+					res = handler.apply(this, args);
+				}
+				return res;
+			} as (typeof UIApplicationDelegate.prototype)[T];
+
+			// store the handlers
+			this._delegateHandlers.set(methodName, handlers);
+		}
+
+		handlers.push(handler);
+	}
+
 	getNativeApplication() {
 		return this.nativeApp;
 	}