Add support for dynamic nesting key serialization. closes #684

Code/ObjectMapping/RKMappingOperation.m

@@ -418,7 +418,7 @@ static BOOL RKObjectContainsValueForKeyPaths(id representation, NSArray *keyPath
     for (RKAttributeMapping *attributeMapping in attributeMappings) {
         if ([self isCancelled]) return NO;
         
-        if ([attributeMapping.sourceKeyPath isEqualToString:RKObjectMappingNestingAttributeKeyName]) {
+        if ([attributeMapping.sourceKeyPath isEqualToString:RKObjectMappingNestingAttributeKeyName] || [attributeMapping.destinationKeyPath isEqualToString:RKObjectMappingNestingAttributeKeyName]) {
             RKLogTrace(@"Skipping attribute mapping for special keyPath '%@'", attributeMapping.sourceKeyPath);
             continue;
         }
@@ -714,18 +714,31 @@ static BOOL RKObjectContainsValueForKeyPaths(id representation, NSArray *keyPath
 
 - (void)applyNestedMappings
 {
-    RKAttributeMapping *attributeMapping = [self.objectMapping attributeMappingForKeyOfRepresentation];
+    RKAttributeMapping *attributeMapping = [self.objectMapping mappingForSourceKeyPath:RKObjectMappingNestingAttributeKeyName];
     if (attributeMapping) {
         RKLogDebug(@"Found nested mapping definition to attribute '%@'", attributeMapping.destinationKeyPath);
         id attributeValue = [[self.sourceObject allKeys] lastObject];
         if (attributeValue) {
             RKLogDebug(@"Found nesting value of '%@' for attribute '%@'", attributeValue, attributeMapping.destinationKeyPath);
-            _nestedAttributeSubstitution = [[NSDictionary alloc] initWithObjectsAndKeys:attributeValue, attributeMapping.destinationKeyPath, nil];
+            _nestedAttributeSubstitution = @{ attributeMapping.destinationKeyPath: attributeValue };
             [self applyAttributeMapping:attributeMapping withValue:attributeValue];
         } else {
             RKLogWarning(@"Unable to find nesting value for attribute '%@'", attributeMapping.destinationKeyPath);
         }
     }
+    
+    // Serialization
+    attributeMapping = [self.objectMapping mappingForDestinationKeyPath:RKObjectMappingNestingAttributeKeyName];
+    if (attributeMapping) {
+        RKLogDebug(@"Found nested mapping definition to attribute '%@'", attributeMapping.destinationKeyPath);
+        id attributeValue = [self.sourceObject valueForKeyPath:attributeMapping.sourceKeyPath];
+        if (attributeValue) {
+            RKLogDebug(@"Found nesting value of '%@' for attribute '%@'", attributeValue, attributeMapping.sourceKeyPath);
+            _nestedAttributeSubstitution = @{ attributeMapping.sourceKeyPath: attributeValue };
+        } else {
+            RKLogWarning(@"Unable to find nesting value for attribute '%@'", attributeMapping.destinationKeyPath);
+        }
+    }
 }
 
 - (void)cancel

Code/ObjectMapping/RKObjectMapping.h

@@ -96,9 +96,9 @@
  */
 + (instancetype)requestMapping;
 
-///---------------------------------
-/// @name Managing Property Mappings
-///---------------------------------
+///----------------------------------
+/// @name Accessing Property Mappings
+///----------------------------------
 
 /**
  The aggregate collection of attribute and relationship mappings within this object mapping.
@@ -109,6 +109,7 @@
  Returns the property mappings of the receiver in a dictionary, where the keys are the source key paths and the values are instances of `RKAttributeMapping` or `RKRelationshipMapping`.
  
  @return The property mappings of the receiver in a dictionary, where the keys are the source key paths and the values are instances of `RKAttributeMapping` or `RKRelationshipMapping`.
+ @warning Note this method does not return any property mappings with a `nil` value for the source key path in the dictionary returned.
  */
 @property (nonatomic, readonly) NSDictionary *propertyMappingsBySourceKeyPath;
 
@@ -116,6 +117,7 @@
  Returns the property mappings of the receiver in a dictionary, where the keys are the destination key paths and the values are instances of `RKAttributeMapping` or `RKRelationshipMapping`.
  
  @return The property mappings of the receiver in a dictionary, where the keys are the destination key paths and the values are instances of `RKAttributeMapping` or `RKRelationshipMapping`.
+ @warning Note this method does not return any property mappings with a `nil` value for the source key path in the dictionary returned.
  */
 @property (nonatomic, readonly) NSDictionary *propertyMappingsByDestinationKeyPath;
 
@@ -129,6 +131,24 @@
  */
 @property (nonatomic, readonly) NSArray *relationshipMappings;
 
+/**
+ Returns the property mapping registered with the receiver with the given source key path.
+ 
+ @param sourceKeyPath The key path to retrieve.
+ */
+- (id)mappingForSourceKeyPath:(NSString *)sourceKeyPath;
+
+/**
+ Returns the property mapping registered with the receiver with the given destinationKeyPath key path.
+ 
+ @param destinationKeyPath The key path to retrieve.
+ */
+- (id)mappingForDestinationKeyPath:(NSString *)destinationKeyPath;
+
+///---------------------------
+/// Managing Property Mappings
+///---------------------------
+
 /**
  Adds a property mapping to the receiver.
 
@@ -226,14 +246,26 @@
 - (void)addAttributeMappingFromKeyOfRepresentationToAttribute:(NSString *)attributeName;
 
 /**
- Returns the attribute mapping targeting the key of a nested dictionary in the source JSON.
+ Adds an attribute mapping to a dynamic nesting key from an attribute. The mapped attribute name can then be referenced wthin other attribute mappings to map content under the nesting key path.
+ 
+ For example, consider that we wish to map a local user object with the properties 'id', 'firstName' and 'email':
+ 
+    RKUser *user = [RKUser new];
+    user.firstName = @"blake";
+    user.userID = @(1234);
+    user.email = @"blake@restkit.org";
 
- This attribute mapping corresponds to the attributeName configured via `mapKeyOfNestedDictionaryToAttribute:`
-
- @return An attribute mapping for the key of a nested dictionary being mapped or nil
- @see `addAttributeMappingFromKeyOfRepresentationToAttribute:`
+ And we wish to map it into JSON that looks like:
+ 
+    { "blake": { "id": 1234, "email": "blake@restkit.org" } }
+ 
+ We can configure our request mapping to handle this like so:
+ 
+     RKObjectMapping *mapping = [RKObjectMapping requestMapping];
+     [mapping addAttributeMappingToKeyOfRepresentationFromAttribute:@"firstName"];
+     [mapping addAttributeMappingsFromDictionary:@{ @"(firstName).userID": @"id", @"(firstName).email": @"email" }];
  */
-- (RKAttributeMapping *)attributeMappingForKeyOfRepresentation;
+- (void)addAttributeMappingToKeyOfRepresentationFromAttribute:(NSString *)attributeName;
 
 ///----------------------------------
 /// @name Configuring Mapping Options

Code/ObjectMapping/RKObjectMapping.m

@@ -175,6 +175,7 @@ static RKSourceToDesinationKeyTransformationBlock defaultSourceToDestinationKeyT
 {
     NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithCapacity:[self.propertyMappings count]];
     for (RKPropertyMapping *propertyMapping in self.propertyMappings) {
+        if (! propertyMapping.sourceKeyPath) continue;
         [dictionary setObject:propertyMapping forKey:propertyMapping.sourceKeyPath];
     }
     
@@ -185,6 +186,7 @@ static RKSourceToDesinationKeyTransformationBlock defaultSourceToDestinationKeyT
 {
     NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithCapacity:[self.propertyMappings count]];
     for (RKPropertyMapping *propertyMapping in self.propertyMappings) {
+        if (! propertyMapping.destinationKeyPath) continue;
         [dictionary setObject:propertyMapping forKey:propertyMapping.destinationKeyPath];
     }
     
@@ -244,11 +246,6 @@ static RKSourceToDesinationKeyTransformationBlock defaultSourceToDestinationKeyT
             NSStringFromClass([self class]), self, NSStringFromClass(self.objectClass), self.propertyMappings];
 }
 
-- (id)mappingForKeyPath:(NSString *)keyPath
-{
-    return [self mappingForSourceKeyPath:keyPath];
-}
-
 - (id)mappingForSourceKeyPath:(NSString *)sourceKeyPath
 {
     for (RKPropertyMapping *mapping in self.propertyMappings) {
@@ -339,9 +336,9 @@ static RKSourceToDesinationKeyTransformationBlock defaultSourceToDestinationKeyT
     [self addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:RKObjectMappingNestingAttributeKeyName toKeyPath:attributeName]];
 }
 
-- (RKAttributeMapping *)attributeMappingForKeyOfRepresentation
+- (void)addAttributeMappingToKeyOfRepresentationFromAttribute:(NSString *)attributeName
 {
-    return [self mappingForKeyPath:RKObjectMappingNestingAttributeKeyName];
+    [self addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:attributeName toKeyPath:RKObjectMappingNestingAttributeKeyName]];
 }
 
 - (RKAttributeMapping *)mappingForAttribute:(NSString *)attributeKey

Tests/Logic/ObjectMapping/RKObjectParameterizationTest.m

@@ -448,6 +448,21 @@
     expect(string).to.equal(@"{\"name\":\"Blake Watters\",\"happy\":false}");
 }
 
+- (void)testSerializingWithDynamicNestingAttribute
+{
+    NSDictionary *object = @{ @"name" : @"blake", @"occupation" : @"Hacker" };
+    RKObjectMapping *mapping = [RKObjectMapping requestMapping];
+    [mapping addAttributeMappingToKeyOfRepresentationFromAttribute:@"name"];
+    [mapping addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:@"name" toKeyPath:@"(name).name"]];
+    [mapping addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:@"occupation" toKeyPath:@"(name).job"]];
+    
+    NSError *error = nil;
+    RKRequestDescriptor *requestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:mapping objectClass:[NSDictionary class] rootKeyPath:nil];
+    NSDictionary *parameters = [RKObjectParameterization parametersWithObject:object requestDescriptor:requestDescriptor error:&error];
+    NSDictionary *expected = @{@"blake": @{@"name": @"blake", @"job": @"Hacker"}};
+    expect(parameters).to.equal(expected);
+}
+
 @end
 
 #pragma mark - Dynamic Request Paramterization