1 files changed, 47 insertions, 0 deletions
diff --git a/Firebase/Core/FIRAppAssociationRegistration.m b/Firebase/Core/FIRAppAssociationRegistration.m
new file mode 100644
index 0000000..a36396d
--- /dev/null
+++ b/Firebase/Core/FIRAppAssociationRegistration.m
@@ -0,0 +1,47 @@
+// Copyright 2017 Google
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "Private/FIRAppAssociationRegistration.h"
+
+#import <objc/runtime.h>
+
+@implementation FIRAppAssociationRegistration
+
++ (nullable id)registeredObjectWithHost:(id)host
+                                    key:(NSString *)key
+                          creationBlock:(id _Nullable (^)())creationBlock {
+  @synchronized(self) {
+    SEL dictKey = @selector(registeredObjectWithHost:key:creationBlock:);
+    NSMutableDictionary<NSString *, id> *objectsByKey = objc_getAssociatedObject(host, dictKey);
+    if (!objectsByKey) {
+      objectsByKey = [[NSMutableDictionary alloc] init];
+      objc_setAssociatedObject(host, dictKey, objectsByKey, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+    }
+    id obj = objectsByKey[key];
+    NSValue *creationBlockBeingCalled = [NSValue valueWithPointer:dictKey];
+    if (obj) {
+      if ([creationBlockBeingCalled isEqual:obj]) {
+        [NSException raise:@"Reentering registeredObjectWithHost:key:creationBlock: not allowed"
+                    format:@"host: %@ key: %@", host, key];
+      }
+      return obj;
+    }
+    objectsByKey[key] = creationBlockBeingCalled;
+    obj = creationBlock();
+    objectsByKey[key] = obj;
+    return obj;
+  }
+}
+
+@end