Break out reused functions for object mapping introspection into RKObjectUtilities

Code/ObjectMapping/RKObjectUtilities.m

@@ -0,0 +1,73 @@
+//
+//  RKObjectUtilities.m
+//  RestKit
+//
+//  Created by Blake Watters on 9/30/12.
+//  Copyright (c) 2012 RestKit. All rights reserved.
+//
+//  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 <objc/message.h>
+#import "RKObjectUtilities.h"
+
+BOOL RKObjectIsEqualToObject(id object, id anotherObject) {
+    NSCAssert(object, @"Expected object not to be nil");
+    NSCAssert(anotherObject, @"Expected anotherObject not to be nil");
+    
+    SEL comparisonSelector;
+    if ([object isKindOfClass:[NSString class]] && [anotherObject isKindOfClass:[NSString class]]) {
+        comparisonSelector = @selector(isEqualToString:);
+    } else if ([object isKindOfClass:[NSNumber class]] && [anotherObject isKindOfClass:[NSNumber class]]) {
+        comparisonSelector = @selector(isEqualToNumber:);
+    } else if ([object isKindOfClass:[NSDate class]] && [anotherObject isKindOfClass:[NSDate class]]) {
+        comparisonSelector = @selector(isEqualToDate:);
+    } else if ([object isKindOfClass:[NSArray class]] && [anotherObject isKindOfClass:[NSArray class]]) {
+        comparisonSelector = @selector(isEqualToArray:);
+    } else if ([object isKindOfClass:[NSDictionary class]] && [anotherObject isKindOfClass:[NSDictionary class]]) {
+        comparisonSelector = @selector(isEqualToDictionary:);
+    } else if ([object isKindOfClass:[NSSet class]] && [anotherObject isKindOfClass:[NSSet class]]) {
+        comparisonSelector = @selector(isEqualToSet:);
+    } else {
+        comparisonSelector = @selector(isEqual:);
+    }
+    
+    // Comparison magic using function pointers. See this page for details: http://www.red-sweater.com/blog/320/abusing-objective-c-with-class
+    // Original code courtesy of Greg Parker
+    // This is necessary because isEqualToNumber will return negative integer values that aren't coercable directly to BOOL's without help [sbw]
+    BOOL (*ComparisonSender)(id, SEL, id) = (BOOL (*)(id, SEL, id))objc_msgSend;
+    return ComparisonSender(object, comparisonSelector, anotherObject);
+}
+
+BOOL RKClassIsCollection(Class aClass)
+{
+    return (aClass && ([aClass isSubclassOfClass:[NSSet class]] ||
+                       [aClass isSubclassOfClass:[NSArray class]] ||
+                       [aClass isSubclassOfClass:[NSOrderedSet class]]));
+}
+
+BOOL RKObjectIsCollection(id object)
+{
+    return RKClassIsCollection([object class]);
+}
+
+BOOL RKObjectIsCollectionContainingOnlyManagedObjects(id object)
+{
+    if (! RKObjectIsCollection(object)) return NO;
+    Class managedObjectClass = NSClassFromString(@"NSManagedObject");
+    if (! managedObjectClass) return NO;
+    for (id instance in object) {
+        if (! [object isKindOfClass:managedObjectClass]) return NO;
+    }
+    return YES;
+}