iOS: Allow specifying your AppDelegate class's name in the Info.plist file.

app/src/util_ios.mm

@@ -27,6 +27,9 @@
 #import <UIKit/UIKit.h>
 #import <objc/runtime.h>
 
+// Key used in Info.plist to specify a custom AppDelegate class name.
+static NSString *const kFirebaseAppDelegateClassNameKey = @"FirebaseAppDelegateClassName";
+
 #define MAX_PENDING_APP_DELEGATE_BLOCKS 8
 #define MAX_SEEN_DELEGATE_CLASSES 32
 
@@ -163,6 +166,55 @@ @implementation UIApplication (FirebaseAppDelegateSwizzling)
 + (void)load {
   static dispatch_once_t onceToken;
   dispatch_once(&onceToken, ^{
+    NSString *appDelegateClassName = [[NSBundle mainBundle] objectForInfoDictionaryKey:kFirebaseAppDelegateClassNameKey];
+
+    if (appDelegateClassName && [appDelegateClassName isKindOfClass:[NSString class]] && appDelegateClassName.length > 0) {
+      Class specificClass = NSClassFromString(appDelegateClassName);
+      if (specificClass) {
+        NSLog(@"Firebase: Info.plist key '%@' found. Targeting AppDelegate class: %@. Swizzling of [UIApplication setDelegate:] will be skipped.",
+              kFirebaseAppDelegateClassNameKey, appDelegateClassName);
+
+        // Set this class as the sole "seen" delegate for Firebase processing.
+        // g_seen_delegate_classes_count should be 0 here in +load, but clear just in case.
+        for (int i = 0; i < g_seen_delegate_classes_count; i++) {
+            g_seen_delegate_classes[i] = nil;
+        }
+        g_seen_delegate_classes[0] = specificClass;
+        g_seen_delegate_classes_count = 1;
+        NSLog(@"Firebase: %@ is now the only delegate class Firebase will initially process.", appDelegateClassName);
+
+        // If there are already blocks pending (e.g., from other Firebase components' +load methods),
+        // execute them now for the specified delegate. These blocks will remain in the pending
+        // queue, mirroring the behavior of the original swizzled setDelegate: method which also
+        // does not clear pending blocks after execution (as they might apply to future delegates).
+        // In this Info.plist mode, however, Firebase won't process further setDelegate: calls.
+        if (g_pending_block_count > 0) {
+          NSLog(@"Firebase: +load (Info.plist Mode) - Executing %d PENDING block(s) for specified delegate: %@. (Blocks are not removed from queue).",
+                g_pending_block_count, NSStringFromClass(specificClass));
+          for (int i = 0; i < g_pending_block_count; i++) {
+            if (g_pending_app_delegate_blocks[i]) {
+              g_pending_app_delegate_blocks[i](specificClass);
+            }
+          }
+          NSLog(@"Firebase: +load (Info.plist Mode) - Pending blocks executed for specific delegate.");
+        }
+        // Skip swizzling. g_original_setDelegate_imp remains NULL.
+        return;
+      } else {
+        NSLog(@"Firebase Error: Info.plist key '%@' specifies class '%@', which was not found. Proceeding with default [UIApplication setDelegate:] swizzling.",
+              kFirebaseAppDelegateClassNameKey, appDelegateClassName);
+      }
+    } else {
+      if (appDelegateClassName) { // Key is present but value is invalid (e.g., empty string or wrong type).
+        NSLog(@"Firebase Warning: Info.plist key '%@' has an invalid value ('%@'). Proceeding with default [UIApplication setDelegate:] swizzling.",
+              kFirebaseAppDelegateClassNameKey, appDelegateClassName);
+      } else { // Key is not present.
+        // This is the default case, no special logging needed here beyond the swizzling log itself.
+      }
+    }
+
+    // Standard behavior: Swizzle [UIApplication setDelegate:]
+    NSLog(@"Firebase: Proceeding with swizzling of [UIApplication setDelegate:].");
     Class uiApplicationClass = [UIApplication class];
     SEL originalSelector = @selector(setDelegate:);
     Method originalMethod = class_getInstanceMethod(uiApplicationClass, originalSelector);
@@ -172,18 +224,11 @@ + (void)load {
       return;
     }
 
-    // Replace the original method's implementation with Firebase_setDelegate
-    // and store the original IMP.
     IMP previousImp = method_setImplementation(originalMethod, (IMP)Firebase_setDelegate);
     if (previousImp) {
         g_original_setDelegate_imp = previousImp;
         NSLog(@"Firebase: Successfully swizzled [UIApplication setDelegate:] and stored original IMP.");
     } else {
-        // This would be unusual - method_setImplementation replacing a NULL IMP,
-        // or method_setImplementation itself failed (though it doesn't typically return NULL on failure,
-        // it might return the new IMP or the old one depending on versions/runtime).
-        // More robustly, g_original_setDelegate_imp should be checked before use.
-        // For now, this logging indicates if previousImp was unexpectedly nil.
         NSLog(@"Firebase Error: Swizzled [UIApplication setDelegate:], but original IMP was NULL (or method_setImplementation failed to return the previous IMP).");
     }
   });
@@ -194,6 +239,7 @@ + (void)load {
 namespace firebase {
 namespace util {
 
+// This is the ORIGINAL implementation of RunOnAppDelegateClasses
 void RunOnAppDelegateClasses(void (^block)(Class)) {
   if (g_seen_delegate_classes_count > 0) {
     NSLog(@"Firebase: RunOnAppDelegateClasses executing block for %d already seen delegate class(es).",