1 files changed, 48 insertions, 0 deletions
diff --git a/Firebase/Core/Private/FIRAppAssociationRegistration.h b/Firebase/Core/Private/FIRAppAssociationRegistration.h
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+++ b/Firebase/Core/Private/FIRAppAssociationRegistration.h
@@ -0,0 +1,48 @@
+/*
+ * 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 <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** @class FIRAppAssociationRegistration
+    @brief Manages object associations as a singleton-dependent: At most one object is
+        registered for any given host/key pair, and the object shall be created on-the-fly when
+        asked for.
+ */
+@interface FIRAppAssociationRegistration<ObjectType> : NSObject
+
+/** @fn registeredObjectWithHost:key:creationBlock:
+    @brief Retrieves the registered object with a particular host and key.
+    @param host The host object.
+    @param key The key to specify the registered object on the host.
+    @param creationBlock The block to return the object to be registered if not already.
+        The block is executed immediately before this method returns if it is executed at all.
+        It can also be executed multiple times across different method invocations if previous
+        execution of the block returns @c nil.
+    @return The registered object for the host/key pair, or @c nil if no object is registered
+        and @c creationBlock returns @c nil.
+    @remarks The method is thread-safe but non-reentrant in the sense that attempting to call this
+        method again within the @c creationBlock with the same host/key pair raises an exception.
+        The registered object is retained by the host.
+ */
++ (nullable ObjectType)registeredObjectWithHost:(id)host
+                                            key:(NSString *)key
+                                  creationBlock:(ObjectType _Nullable (^)())creationBlock;
+
+@end
+
+NS_ASSUME_NONNULL_END