Add fix to handling of many-to-many encoding, and test to verify it.

Refactor and fix in `-buy_JSONForValue:` as well as other refactoring. Move a comment to where it is most applicable.

Mobile Buy SDK/Mobile Buy SDK Tests/BUYCoreDataModelAdditionsTests.m

@@ -34,11 +34,12 @@
 #import "NSPropertyDescription+BUYAdditions.h"
 #import "TestModel.h"
 
-static NSString * const RootEntity = @"Root";
+static NSString * const BirdEntity = @"Bird";
 static NSString * const BranchEntity = @"Branch";
 static NSString * const LeafEntity = @"Leaf";
 static NSString * const NestEntity = @"Nest";
-static NSString * const BirdEntity = @"Bird";
+static NSString * const ResearchEntity = @"Researcher";
+static NSString * const RootEntity = @"Root";
 
 @interface NSIndexSet (BUYTestAdditions)
 + (instancetype)indexSetWithIndexes:(NSArray *)indexes;
@@ -228,6 +229,13 @@ static NSString * const BirdEntity = @"Bird";
 	XCTAssertEqualObjects(actual, branch.leaves);
 }
 
+- (void)testManyToManyRelationship
+{
+	Researcher *researcher = [self.modelManager buy_objectWithEntityName:ResearchEntity JSONDictionary:nil];
+	NSRelationshipDescription *researchersRelationship = [self relationshipWithName:@"researchers" forEntity:BirdEntity];
+	XCTAssertNil([researchersRelationship buy_JSONForValue:[NSSet setWithObject:researcher]]);
+}
+
 - (void)testEntityIsPrivate
 {
 	NSEntityDescription *forestEntity = [self entityForName:[Forest entityName]];

Mobile Buy SDK/Mobile Buy SDK Tests/BUYTestModel.xcdatamodeld/BUYTestModel.xcdatamodel/contents

@@ -9,6 +9,7 @@
                 <entry key="key" value="value"/>
             </userInfo>
         </relationship>
+        <relationship name="researchers" optional="YES" toMany="YES" deletionRule="Nullify" destinationEntity="Researcher" inverseName="birds" inverseEntity="Researcher" syncable="YES"/>
     </entity>
     <entity name="Branch" representedClassName="Branch" syncable="YES">
         <attribute name="ornaments" optional="YES" attributeType="Transformable" syncable="YES">
@@ -50,6 +51,10 @@
         </relationship>
         <relationship name="branch" optional="YES" maxCount="1" deletionRule="Nullify" destinationEntity="Branch" inverseName="nest" inverseEntity="Branch" syncable="YES"/>
     </entity>
+    <entity name="Researcher" representedClassName="Researcher" syncable="YES">
+        <attribute name="name" optional="YES" attributeType="String" syncable="YES"/>
+        <relationship name="birds" optional="YES" toMany="YES" deletionRule="Nullify" destinationEntity="Bird" inverseName="researchers" inverseEntity="Bird" syncable="YES"/>
+    </entity>
     <entity name="Root" representedClassName="Root" syncable="YES">
         <attribute name="age" optional="YES" attributeType="Decimal" defaultValueString="0.0" syncable="YES"/>
         <attribute name="identifier" optional="YES" attributeType="Integer 64" defaultValueString="0" syncable="YES"/>
@@ -64,11 +69,12 @@
         <relationship name="forest" optional="YES" maxCount="1" deletionRule="Nullify" destinationEntity="Forest" inverseName="trees" inverseEntity="Forest" syncable="YES"/>
     </entity>
     <elements>
-        <element name="Bird" positionX="151" positionY="111" width="128" height="90"/>
+        <element name="Bird" positionX="146" positionY="111" width="128" height="103"/>
         <element name="Branch" positionX="-288" positionY="-3" width="128" height="105"/>
+        <element name="Forest" positionX="-718" positionY="57" width="128" height="58"/>
         <element name="Leaf" positionX="-72" positionY="-18" width="128" height="90"/>
         <element name="Nest" positionX="-72" positionY="126" width="128" height="90"/>
         <element name="Root" positionX="-504" positionY="-18" width="128" height="133"/>
-        <element name="Forest" positionX="-477" positionY="137" width="128" height="58"/>
+        <element name="Researcher" positionX="-288" positionY="81" width="128" height="75"/>
     </elements>
 </model>
\ No newline at end of file

Mobile Buy SDK/Mobile Buy SDK Tests/TestModel.h

@@ -20,11 +20,12 @@
 @property (nonatomic, strong) TestModelManager *modelManager;
 @end
 
-@class Leaf, Nest, Root;
+@class Leaf, Nest, Researcher, Root;
 
 @interface Bird : TestModel
 @property (nonatomic) NSNumber *identifier;
 @property (nonatomic) NSString *colour;
+@property (nonatomic) NSSet<Researcher *> *researchers;
 + (instancetype)birdWithIdentifier:(NSNumber *)identifier;
 @end
 
@@ -49,6 +50,11 @@
 @property (nonatomic) Branch *branch;
 @end
 
+@interface Researcher : TestModel
+@property (nonatomic) NSString *name;
+@property (nonatomic) NSSet<Bird *> *birds;
+@end
+
 @interface Root : TestModel
 @property (nonatomic) NSNumber *identifier;
 @property (nonatomic) NSDecimalNumber *age;

Mobile Buy SDK/Mobile Buy SDK Tests/TestModel.m

@@ -200,9 +200,7 @@
 
 - (NSUInteger)hash
 {
-	NSUInteger hash = self.date.hash;
-	hash = (hash << 5) ^ self.tags.hash;
-	return hash;
+	return (self.date.hash << 5) ^ self.tags.hash;
 }
 
 @end
@@ -218,11 +216,22 @@
 
 - (NSUInteger)hash
 {
-	NSUInteger hash = self.eggCount.hash;
-	if (self.bird) {
-		hash = (hash << 5) ^ self.bird.hash;
-	}
-	return hash;
+	return (self.branch.hash << 5) ^ (7231UL + self.eggCount.unsignedIntegerValue);
+}
+
+@end
+
+@implementation Researcher
+
+- (BOOL)isEqual:(Researcher *)object
+{
+	return ([super isEqual:object] &&
+			[self.name isEqual:object.name]);
+}
+
+- (NSUInteger)hash
+{
+	return self.name.hash;
 }
 
 @end
@@ -241,12 +250,7 @@
 
 - (NSUInteger)hash
 {
-	NSUInteger hash = self.identifier.hash;
-	hash = (hash << 5) ^ self.age.hash;
-	hash = (hash << 5) ^ self.name.hash;
-	hash = (hash << 5) ^ self.url.hash;
-	hash = (hash << 5) ^ self.branches.hash;
-	return hash;
+	return self.identifier.hash;
 }
 
 @end

Mobile Buy SDK/Mobile Buy SDK/Additions/NSPropertyDescription+BUYAdditions.m

@@ -200,14 +200,6 @@ static NSString *JSONValueTransformerNameForAttributeType(NSAttributeType type)
 // model -> JSON
 - (id)buy_JSONForObject:(NSObject<BUYObject> *)object
 {
-	// JSON generation for a relationship depends on the rules defined in the model.
-	// The model can explicitly specify using an `id` encoding.
-	// Alternately, if the relationship is compatible, encode the entire object.
-	// We do not encode related objects unless three conditions are satisfied:
-	// 1. the relationship is not many-to-many
-	// 2. the inverse relationship is not an ownership relationship
-	//    (this is inferred from the `NSCascadeDeleteRule` used by owning objects)
-	// 3. the relationship is to a "private" entity (not known to the API)
 	id json = nil;
 	if (!self.inverseRelationship || self.inverseRelationship.allowsInverseEncoding) {
 		json = [self.destinationEntity buy_JSONForObject:object];
@@ -238,8 +230,7 @@ static NSString *JSONValueTransformerNameForAttributeType(NSAttributeType type)
 // (ordered)set (of models) -> JSON
 - (NSArray *)buy_JSONForCollection:(id)collection
 {
-	NSArray *array = [self buy_arrayForCollection:collection];
-	return [self.destinationEntity buy_JSONForArray:array];
+	return [self.destinationEntity buy_JSONForArray:[self buy_arrayForCollection:collection]];
 }
 
 #pragma mark - Property Additions Overrides
@@ -250,31 +241,38 @@ static NSString *JSONValueTransformerNameForAttributeType(NSAttributeType type)
 	// The logic for decoding JSON is slightly different for to-one and to-many relationships.
 	
 	// NOTE: by default, without a caching system, inverse relationships are not supported.
+	id value = nil;
 	if ([JSON buy_isValidObject]) {
 		if (self.isToMany) {
-			return [self buy_collectionForJSON:JSON modelManager:object.modelManager];
+			value = [self buy_collectionForJSON:JSON modelManager:object.modelManager];
 		}
 		else {
-			return [self buy_objectForJSON:JSON modelManager:object.modelManager];
+			value = [self buy_objectForJSON:JSON modelManager:object.modelManager];
 		}
 	}
-	else {
-		return nil;
-	}
+	return value;
 }
 
 - (id)buy_JSONForValue:(id)value
 {
+	// JSON generation for a relationship depends on the rules defined in the model.
+	// The model can explicitly specify using an `id` encoding.
+	// Alternately, if the relationship is compatible, encode the entire object.
+	// We do not encode related objects unless three conditions are satisfied:
+	// 1. the relationship is not many-to-many
+	// 2. the inverse relationship is not an ownership relationship
+	//    (this is inferred from the `NSCascadeDeleteRule` used by owning objects)
+	// 3. the relationship is to a "private" entity (not known to the API)
 	id json = nil;
 	if (self.encodesIdInJSON) {
 		json = [value valueForKey:NSStringFromSelector(@selector(identifier))];
 	}
-	else if (self.toMany && ! self.manyToMany) {
-		json = [self buy_JSONForCollection:value];
-	}
-	else {
+	else if (!self.toMany) {
 		json = [self buy_JSONForObject:value];
 	}
+	else if (!self.manyToMany) {
+		json = [self buy_JSONForCollection:value];
+	}
 	return json;
 }