Update BUYObject class to adopt BUYObject protocol.

Also update to support new JSON serialization and dirty tracking.

Mobile Buy SDK/Mobile Buy SDK Tests/BUYObjectTests.m

@@ -175,11 +175,9 @@
 
 @implementation BUYDirtyTracked
 
-+ (void)initialize
++ (BOOL)tracksDirtyProperties
 {
-	if (self == [BUYDirtyTracked class]) {
-		[self trackDirtyProperties];
-	}
+	return YES;
 }
 
 @end

Mobile Buy SDK/Mobile Buy SDK.xcodeproj/project.pbxproj

@@ -87,6 +87,10 @@
 		84980F2A1CB75AC200CFAB58 /* BUYObjectProtocol.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F281CB75AC200CFAB58 /* BUYObjectProtocol.h */; };
 		84980F2C1CB75B5E00CFAB58 /* BUYModelManagerProtocol.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F2B1CB75B5E00CFAB58 /* BUYModelManagerProtocol.h */; };
 		84980F2D1CB75B5E00CFAB58 /* BUYModelManagerProtocol.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F2B1CB75B5E00CFAB58 /* BUYModelManagerProtocol.h */; };
+		84980F291CB75AC200CFAB58 /* BUYObjectProtocol.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F281CB75AC200CFAB58 /* BUYObjectProtocol.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		84980F2A1CB75AC200CFAB58 /* BUYObjectProtocol.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F281CB75AC200CFAB58 /* BUYObjectProtocol.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		84980F2C1CB75B5E00CFAB58 /* BUYModelManagerProtocol.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F2B1CB75B5E00CFAB58 /* BUYModelManagerProtocol.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		84980F2D1CB75B5E00CFAB58 /* BUYModelManagerProtocol.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F2B1CB75B5E00CFAB58 /* BUYModelManagerProtocol.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		84980F321CB75C2900CFAB58 /* NSEntityDescription+BUYAdditions.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F2E1CB75C2900CFAB58 /* NSEntityDescription+BUYAdditions.h */; };
 		84980F331CB75C2900CFAB58 /* NSEntityDescription+BUYAdditions.h in Headers */ = {isa = PBXBuildFile; fileRef = 84980F2E1CB75C2900CFAB58 /* NSEntityDescription+BUYAdditions.h */; };
 		84980F341CB75C2900CFAB58 /* NSEntityDescription+BUYAdditions.m in Sources */ = {isa = PBXBuildFile; fileRef = 84980F2F1CB75C2900CFAB58 /* NSEntityDescription+BUYAdditions.m */; };
@@ -119,6 +123,10 @@
 		849810971CB7E07900CFAB58 /* BUYFlatCollectionTransformer.h in Headers */ = {isa = PBXBuildFile; fileRef = 849810901CB7E07900CFAB58 /* BUYFlatCollectionTransformer.h */; };
 		849810981CB7E07900CFAB58 /* BUYFlatCollectionTransformer.m in Sources */ = {isa = PBXBuildFile; fileRef = 849810911CB7E07900CFAB58 /* BUYFlatCollectionTransformer.m */; };
 		849810991CB7E07900CFAB58 /* BUYFlatCollectionTransformer.m in Sources */ = {isa = PBXBuildFile; fileRef = 849810911CB7E07900CFAB58 /* BUYFlatCollectionTransformer.m */; };
+		84D915431CC0359700D334FB /* BUYObserver.h in Headers */ = {isa = PBXBuildFile; fileRef = 84D915411CC0359700D334FB /* BUYObserver.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		84D915441CC0359700D334FB /* BUYObserver.h in Headers */ = {isa = PBXBuildFile; fileRef = 84D915411CC0359700D334FB /* BUYObserver.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		84D915451CC0359700D334FB /* BUYObserver.m in Sources */ = {isa = PBXBuildFile; fileRef = 84D915421CC0359700D334FB /* BUYObserver.m */; };
+		84D915461CC0359700D334FB /* BUYObserver.m in Sources */ = {isa = PBXBuildFile; fileRef = 84D915421CC0359700D334FB /* BUYObserver.m */; };
 		9003969B1B601DF400226B73 /* BUYCartLineItem.h in Headers */ = {isa = PBXBuildFile; fileRef = 900396991B601DF400226B73 /* BUYCartLineItem.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		9003969C1B601DF400226B73 /* BUYCartLineItem.m in Sources */ = {isa = PBXBuildFile; fileRef = 9003969A1B601DF400226B73 /* BUYCartLineItem.m */; };
 		900396AC1B627CB900226B73 /* BUYProductView.h in Headers */ = {isa = PBXBuildFile; fileRef = 900396AA1B627CB900226B73 /* BUYProductView.h */; };
@@ -467,6 +475,8 @@
 		8498108F1CB7E07900CFAB58 /* BUYDeliveryRangeTransformer.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = BUYDeliveryRangeTransformer.m; sourceTree = "<group>"; };
 		849810901CB7E07900CFAB58 /* BUYFlatCollectionTransformer.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BUYFlatCollectionTransformer.h; sourceTree = "<group>"; };
 		849810911CB7E07900CFAB58 /* BUYFlatCollectionTransformer.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = BUYFlatCollectionTransformer.m; sourceTree = "<group>"; };
+		84D915411CC0359700D334FB /* BUYObserver.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BUYObserver.h; sourceTree = "<group>"; };
+		84D915421CC0359700D334FB /* BUYObserver.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = BUYObserver.m; sourceTree = "<group>"; };
 		900396991B601DF400226B73 /* BUYCartLineItem.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BUYCartLineItem.h; sourceTree = "<group>"; };
 		9003969A1B601DF400226B73 /* BUYCartLineItem.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = BUYCartLineItem.m; sourceTree = "<group>"; };
 		900396AA1B627CB900226B73 /* BUYProductView.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; lineEnding = 0; name = BUYProductView.h; path = "Product View/BUYProductView.h"; sourceTree = "<group>"; xcLanguageSpecificationIdentifier = xcode.lang.objcpp; };
@@ -972,6 +982,8 @@
 				BE47340E1B66C4EF00AA721A /* BUYError.m */,
 				2AF52A931A7010B20087DB2C /* BUYObject.h */,
 				2AF52A941A7010B20087DB2C /* BUYObject.mm */,
+				84D915411CC0359700D334FB /* BUYObserver.h */,
+				84D915421CC0359700D334FB /* BUYObserver.m */,
 				F76CFF1E19CB7C500079C703 /* BUYSerializable.h */,
 			);
 			path = Models;
@@ -1108,6 +1120,7 @@
 				901931571BC5B9BC00D1134E /* BUYObject.h in Headers */,
 				901931581BC5B9BC00D1134E /* BUYRuntime.h in Headers */,
 				901931591BC5B9BC00D1134E /* BUYCollection.h in Headers */,
+				84D915441CC0359700D334FB /* BUYObserver.h in Headers */,
 				9019315A1BC5B9BC00D1134E /* BUYProductImageCollectionViewCell.h in Headers */,
 				84980F5F1CB7617E00CFAB58 /* BUYDateTransformer.h in Headers */,
 				84980F591CB7617500CFAB58 /* BUYURLTransformer.h in Headers */,
@@ -1197,6 +1210,7 @@
 				BE9A645D1B503CE30033E558 /* BUYObject.h in Headers */,
 				BE9A646E1B503D1E0033E558 /* BUYRuntime.h in Headers */,
 				BEB74A901B55A3D00005A300 /* BUYCollection.h in Headers */,
+				84D915431CC0359700D334FB /* BUYObserver.h in Headers */,
 				904606AF1B6BC8D700754173 /* BUYProductImageCollectionViewCell.h in Headers */,
 				84980F5E1CB7617E00CFAB58 /* BUYDateTransformer.h in Headers */,
 				84980F581CB7617500CFAB58 /* BUYURLTransformer.h in Headers */,
@@ -1416,6 +1430,7 @@
 				901930FD1BC5B9BC00D1134E /* BUYTaxLine.m in Sources */,
 				901930FE1BC5B9BC00D1134E /* BUYCollection+Additions.m in Sources */,
 				84980F351CB75C2900CFAB58 /* NSEntityDescription+BUYAdditions.m in Sources */,
+				84D915461CC0359700D334FB /* BUYObserver.m in Sources */,
 				901930FF1BC5B9BC00D1134E /* BUYVariantOptionBreadCrumbsView.m in Sources */,
 				901931011BC5B9BC00D1134E /* BUYTheme+Additions.m in Sources */,
 				901931021BC5B9BC00D1134E /* BUYStoreViewController.m in Sources */,
@@ -1531,6 +1546,7 @@
 				BE9A64521B503CB80033E558 /* BUYTaxLine.m in Sources */,
 				900396F71B69563400226B73 /* BUYCollection+Additions.m in Sources */,
 				84980F341CB75C2900CFAB58 /* NSEntityDescription+BUYAdditions.m in Sources */,
+				84D915451CC0359700D334FB /* BUYObserver.m in Sources */,
 				90DE92711B9897B6002EF4DA /* BUYVariantOptionBreadCrumbsView.m in Sources */,
 				906EAE441B836DE000976165 /* BUYTheme+Additions.m in Sources */,
 				BE9A647F1B503D960033E558 /* BUYStoreViewController.m in Sources */,

Mobile Buy SDK/Mobile Buy SDK/Buy.h

@@ -57,6 +57,9 @@ FOUNDATION_EXPORT const unsigned char BuyVersionString[];
 #import <Buy/BUYApplePayHelpers.h>
 #import <Buy/BUYClient.h>
 #import <Buy/BUYError.h>
+#import <Buy/BUYModelManagerProtocol.h>
+#import <Buy/BUYObjectProtocol.h>
+#import <Buy/BUYObserver.h>
 
 #import <Buy/BUYPaymentButton.h>
 #import <Buy/BUYProductViewController.h>

Mobile Buy SDK/Mobile Buy SDK/Models/BUYModelManagerProtocol.h

@@ -26,6 +26,8 @@
 
 #import <CoreData/CoreData.h>
 
+@protocol BUYObject;
+
 /**
  * A protocol for defining an object that can store and retrieve model objects from a data store or other cache.
  */

Mobile Buy SDK/Mobile Buy SDK/Models/BUYObject.h

@@ -26,6 +26,8 @@
 
 #import <Foundation/Foundation.h>
 
+#import <Buy/BUYObjectProtocol.h>
+
 /**
  *  This is the base class for all Shopify model objects.
  *  This class takes care of convertion .json responses into
@@ -33,7 +35,7 @@
  *
  *  You will generally not need to interact with this class directly.
  */
-@interface BUYObject : NSObject
+@interface BUYObject : NSObject<BUYObject>
 
 /**
  *  The identifier of any Shopify model object.
@@ -59,6 +61,5 @@
 - (NSSet *)dirtyProperties;
 - (void)markPropertyAsDirty:(NSString *)property;
 - (void)markAsClean;
-+ (void)trackDirtyProperties;
 
 @end

Mobile Buy SDK/Mobile Buy SDK/Models/BUYObject.mm

@@ -25,37 +25,21 @@
 //
 
 #import "BUYObject.h"
+#import "BUYModelManagerProtocol.h"
+#import "BUYObserver.h"
 #import "BUYRuntime.h"
-#import <objc/runtime.h>
-#import <objc/message.h>
+#import "NSDictionary+BUYAdditions.h"
+#import "NSException+BUYAdditions.h"
+#import "NSEntityDescription+BUYAdditions.h"
 
-namespace shopify
-{
-	namespace mobilebuysdk
-	{
-		/**
-		 * Creates and returns a block that is used as the setter method for the persisted subclasses
-		 * The method implementation calls through to its superclasses implementation and then marks
-		 * the attribute as dirty.
-		 */
-		template <typename T>
-		id attribute_setter(NSString *propertyName, SEL selector)
-		{
-			id setterBlock = ^ void (id _self, T value) {
-				// we need to cast objc_msgSend so that the compiler inserts proper type information for the passed in value
-				// not doing so results in strange behaviour (for example, floats never get set)
-				void (*typed_objc_msgSend)(id, SEL, T) = (void (*)(id, SEL, T))objc_msgSend;
-				typed_objc_msgSend(_self, selector, value);
-				[_self markPropertyAsDirty:propertyName];
-			};
-			return setterBlock;
-		}
-	}
-}
+@interface BUYObject ()
+@property (nonatomic, readwrite, weak) id<BUYModelManager> modelManager;
+@property (nonatomic) BUYObserver *dirtyObserver;
+@end
 
-@implementation BUYObject {
-	NSMutableSet *_dirtyProperties;
-}
+@implementation BUYObject
+
+#pragma mark - Deprecated
 
 - (instancetype)init
 {
@@ -64,18 +48,7 @@ namespace shopify
 
 - (instancetype)initWithDictionary:(NSDictionary *)dictionary
 {
-	self = [super init];
-	if (self) {
-		_dirtyProperties = [[NSMutableSet alloc] init];
-		[self updateWithDictionary:dictionary];
-		[self markAsClean];
-	}
-	return self;
-}
-
-- (void)updateWithDictionary:(NSDictionary *)dictionary
-{
-	_identifier = dictionary[@"id"];
+	return [self initWithModelManager:nil JSONDictionary:dictionary];
 }
 
 + (NSArray *)convertJSONArray:(NSArray*)json block:(void (^)(id obj))createdBlock
@@ -109,157 +82,141 @@ namespace shopify
 
 - (BOOL)isDirty
 {
-	return [_dirtyProperties count] > 0;
+	return [self.dirtyObserver hasChanges];
 }
 
 - (NSSet *)dirtyProperties
 {
-	return [NSSet setWithSet:_dirtyProperties];
+	return self.dirtyObserver.changedProperties;
 }
 
 - (void)markPropertyAsDirty:(NSString *)property
 {
-	[_dirtyProperties addObject:property];
+	[self.dirtyObserver markPropertyChanged:property];
 }
 
 - (void)markAsClean
 {
-	[_dirtyProperties removeAllObjects];
+	[self.dirtyObserver reset];
 }
 
-+ (id)setterBlockForSelector:(SEL)selector property:(NSString *)property typeEncoding:(const char *)typeEncoding
+- (BOOL)isEqual:(id)object
 {
-	id setterBlock;
-	switch (typeEncoding[0]) {
-		case '@': // object
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<id>(property, selector);
-			break;
-		}
-		case 'B': // C++ style bool/_Bool
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<bool>(property, selector);
-			break;
-		}
-		case 'c': // char
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<char>(property, selector);
-			break;
-		}
-		case 'C': // unsigned char
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<unsigned char>(property, selector);
-			break;
-		}
-		case 'i': // int
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<int>(property, selector);
-			break;
-		}
-		case 'I': // unsigned int
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<unsigned int>(property, selector);
-			break;
-		}
-		case 's': // short
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<short>(property, selector);
-			break;
-		}
-		case 'S': // unsigned short
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<unsigned short>(property, selector);
-			break;
-		}
-		case 'l': // long
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<long>(property, selector);
-			break;
-		}
-		case 'L': // unsigned long
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<unsigned long>(property, selector);
-			break;
-		}
-		case 'q': // long long
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<long long>(property, selector);
-			break;
-		}
-		case 'Q': // unsigned long long
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<unsigned long long>(property, selector);
-			break;
-		}
-		case 'f': // float
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<float>(property, selector);
-			break;
-		}
-		case 'd': // double
-		{
-			setterBlock = shopify::mobilebuysdk::attribute_setter<double>(property, selector);
-			break;
-		}
-	}
-	return setterBlock;
+	if (self == object) return YES;
+	
+	if (![object isKindOfClass:self.class]) return NO;
+	
+	BOOL same = ([self.identifier isEqual:((BUYObject*)object).identifier]);
+	
+	return same;
 }
 
-+ (void)wrapProperty:(NSString *)property
+- (NSUInteger)hash
 {
-	SEL setter = NSSelectorFromString([NSString stringWithFormat:@"set%@:", [NSString stringWithFormat:@"%@%@",[[property substringToIndex:1] uppercaseString], [property substringFromIndex:1]]]);
+	NSUInteger hash = [self.identifier hash];
+	return hash;
+}
 
-	//Get the setter. don't worry about readonly properties as they're irrelevant for dirty tracking
-	if (setter && [self instancesRespondToSelector:setter]) {
-		Method setterMethod = class_getInstanceMethod(self, setter);
-		IMP setterImpl = method_getImplementation(setterMethod);
+- (void)trackDirtyProperties:(NSArray *)properties
+{
+	self.dirtyObserver = [BUYObserver observeProperties:properties ofObject:self];
+}
 
-		NSMethodSignature *methodSignature = [self instanceMethodSignatureForSelector:setter];
-		if ([methodSignature numberOfArguments] == 3) {
-			const char *typeEncoding = [methodSignature getArgumentTypeAtIndex:2];
-			SEL newSetter = NSSelectorFromString([NSString stringWithFormat:@"buy_%@", NSStringFromSelector(setter)]);
+#pragma mark - Dynamic JSON Serialization
 
-			id setterBlock = [self setterBlockForSelector:newSetter property:property typeEncoding:typeEncoding];
++ (NSArray *)propertyNames
+{
+	static NSMutableDictionary *namesCache;
+	static dispatch_once_t onceToken;
+	dispatch_once(&onceToken, ^{
+		namesCache = [NSMutableDictionary dictionary];
+	});
 	
-			if (setterBlock) {
-				//Create 'buy_setX:' that uses the existing implementation
-				class_addMethod(self, newSetter, setterImpl, method_getTypeEncoding(setterMethod));
+	NSString *className = NSStringFromClass(self);
+	NSArray *names = namesCache[className];
+	if (names == nil) {
+		NSMutableSet *allNames = [class_getBUYProperties(self) mutableCopy];
+		[allNames removeObject:NSStringFromSelector(@selector(dirtyObserver))];
+		names = [allNames allObjects];
+		namesCache[className] = names;
+	}
 	
-				//Create a new impmlementation
-				IMP newImpl = imp_implementationWithBlock(setterBlock);
+	return names;
+}
 
-				//Then attach that implementation to 'setX:'. This way calling 'setX:' calls our implementation, and 'buy_setX:' calls the original implementation.
-				class_replaceMethod(self, setter, newImpl, method_getTypeEncoding(setterMethod));
-			}
-		}
-	}
++ (NSEntityDescription *)entity
+{
+	@throw BUYAbstractMethod();
+}
+
++ (NSString *)entityName
+{
+	@throw BUYAbstractMethod();
 }
 
-+ (void)trackDirtyProperties
+- (NSDictionary *)JSONEncodedProperties
 {
-	NSSet *properties = class_getBUYProperties(self);
-	for (NSString *property in properties) {
-		if ([property length] > 0) {
-			[self wrapProperty:property];
+	return self.entity.JSONEncodedProperties;
+}
+
+- (instancetype)initWithModelManager:(id<BUYModelManager>)modelManager JSONDictionary:(NSDictionary *)dictionary
+{
+	self = [super init];
+	if (self) {
+		self.modelManager = modelManager;
+		[self updateWithDictionary:dictionary];
+		if ([[self class] tracksDirtyProperties]) {
+			[self trackDirtyProperties:[[self class] propertyNames]];
 		}
 	}
+	return self;
 }
 
-- (BOOL)isEqual:(id)object
+- (void)updateWithDictionary:(NSDictionary *)dictionary
 {
-	if (self == object) return YES;
+	_identifier = dictionary[@"id"];
+	[self markAsClean];
+}
 
-	if (![object isKindOfClass:self.class]) return NO;
+- (NSDictionary *)jsonDictionaryForCheckout
+{
+	return self.JSONDictionary;
+}
 
-	BOOL same = ([self.identifier isEqual:((BUYObject*)object).identifier]);
++ (NSPredicate *)fetchPredicateWithJSON:(NSDictionary *)JSONDictionary
+{
+	return nil;
+}
 
-	return same;
++ (BOOL)isPersistentClass
+{
+	return NO;
 }
 
-- (NSUInteger)hash
++ (BOOL)tracksDirtyProperties
 {
-	NSUInteger hash = [self.identifier hash];
-	return hash;
+	return NO;
+}
+
+- (NSEntityDescription *)entity
+{
+	return [self.modelManager buy_entityWithName:[[self class] entityName]];
+}
+
+- (NSDictionary *)JSONDictionary
+{
+	// JSON generation starts in `-buy_JSONForObject`.
+	// Both persistent and transient objects go through this interface.
+	return [self.entity buy_JSONForObject:self];
+}
+
+- (void)setJSONDictionary:(NSDictionary *)JSONDictionary
+{
+	// JSON parsing starts in `-buy_updateObject:withJSON:`.
+	// Both persistent and transient objects go through this interface.
+	if ([JSONDictionary count]) {
+		[self.entity buy_updateObject:self withJSON:JSONDictionary];
+	}
 }
 
 @end

Mobile Buy SDK/Mobile Buy SDK/Models/BUYObjectProtocol.h

@@ -25,6 +25,7 @@
 //
 
 #import <Foundation/Foundation.h>
+#import <CoreData/CoreData.h>
 
 @protocol BUYModelManager;
 
@@ -75,7 +76,7 @@
 /**
  * Use the values in the given dictionary to update properties.
  */
-- (void)updateWithJSONDictionary:(NSDictionary *)dictionary;
+- (void)updateWithDictionary:(NSDictionary *)dictionary;
 
 @optional
 

Mobile Buy SDK/Mobile Buy SDK/Models/BUYObserver.h

+//
+//  BUYObserver.h
+//  Mobile Buy SDK
+//
+//  Created by Shopify.
+//  Copyright (c) 2015 Shopify Inc. All rights reserved.
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in
+//  all copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+//  THE SOFTWARE.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface BUYObserver : NSObject
+
+@property (nonatomic, readonly) NSObject *object;
+@property (nonatomic, readonly) NSArray *observedProperties;
+@property (nonatomic, readonly) NSSet *changedProperties;
+@property (nonatomic, readonly) BOOL hasChanges;
+
+- (instancetype)init NS_UNAVAILABLE;
+- (void)markPropertyChanged:(NSString *)property;
+- (void)reset;
+- (void)cancel;
+
++ (instancetype)observeProperties:(NSArray<NSString *> *)properties ofObject:(id)object;
+
+@end

Mobile Buy SDK/Mobile Buy SDK/Models/BUYObserver.m

+//
+//  BUYObserver.m
+//  Mobile Buy SDK
+//
+//  Created by Shopify.
+//  Copyright (c) 2015 Shopify Inc. All rights reserved.
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in
+//  all copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+//  THE SOFTWARE.
+//
+
+#import "BUYObserver.h"
+
+static void * kBUYObserverContext = &kBUYObserverContext;
+
+@interface BUYObserver ()
+@property (nonatomic) NSObject *object;
+@property (nonatomic) NSArray *observedProperties;
+@end
+
+@implementation BUYObserver {
+	NSMutableSet *_changedProperties;
+}
+
+- (instancetype)initWithObject:(id)object properties:(NSArray<NSString *> *)properties
+{
+	self = [super init];
+	if (self) {
+		self.object = object;
+		self.observedProperties = properties;
+		_changedProperties = [NSMutableSet set];
+		[self startObserving];
+	}
+	return self;
+}
+
+- (void)dealloc
+{
+	[self stopObserving];
+}
+
+#pragma mark - Accessors
+
+- (NSSet *)changedProperties
+{
+	return [_changedProperties copy];
+}
+
+- (void)addChangedPropertiesObject:(NSString *)object
+{
+	[_changedProperties addObject:object];
+}
+
+- (void)removeChangedProperties:(NSSet *)objects
+{
+	[_changedProperties minusSet:objects];
+}
+
+#pragma mark - Key Value Observing
+
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context
+{
+	if (context == kBUYObserverContext) {
+		[self markPropertyChanged:keyPath];
+	}
+	else {
+		[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
+	}
+}
+
+- (void)startObserving
+{
+	for (NSString *property in _observedProperties) {
+		[_object addObserver:self forKeyPath:property options:0 context:kBUYObserverContext];
+	}
+}
+
+- (void)stopObserving
+{
+	for (NSString *property in _observedProperties) {
+		[_object removeObserver:self forKeyPath:property];
+	}
+}
+
+#pragma mark - BUYObserver
+
+- (void)markPropertyChanged:(NSString *)property
+{
+	[self addChangedPropertiesObject:property];
+}
+
+- (BOOL)hasChanges
+{
+	return _changedProperties.count > 0;
+}
+
+- (void)reset {
+	[self removeChangedProperties:[_changedProperties copy]];
+}
+
+- (void)cancel {
+	[self reset];
+	[self stopObserving];
+	_changedProperties = nil;
+	_observedProperties = nil;
+	_object = nil;
+}
+
++ (instancetype)observeProperties:(NSArray<NSString *> *)properties ofObject:(id)object
+{
+	return [[self alloc] initWithObject:object properties:properties];
+}
+
+@end

Mobile Buy SDK/Mobile Buy SDK/Models/BUYSerializable.h

@@ -24,7 +24,7 @@
 //  THE SOFTWARE.
 //
 
-@import Foundation;
+#import <Foundation/Foundation.h>
 
 @protocol BUYSerializable <NSObject>
 

Mobile Buy SDK/Mobile Buy SDK/Models/Persistent/BUYShop.m

@@ -28,13 +28,6 @@
 
 @implementation BUYShop
 
-+ (void)initialize
-{
-	if (self == [BUYShop class]) {
-		[self trackDirtyProperties];
-	}
-}
-
 - (void)updateWithDictionary:(NSDictionary *)dictionary
 {
 	[super updateWithDictionary:dictionary];

Mobile Buy SDK/Mobile Buy SDK/Models/Transient/BUYCheckout.m

@@ -46,11 +46,9 @@
 
 @implementation BUYCheckout
 
-+ (void)initialize
++ (BOOL)tracksDirtyProperties
 {
-	if (self == [BUYCheckout class]) {
-		[self trackDirtyProperties];
-	}
+	return YES;
 }
 
 - (instancetype)initWithCart:(BUYCart *)cart

Mobile Buy SDK/Mobile Buy SDK/Static Framework/Buy.h

@@ -53,6 +53,9 @@
 #import "BUYApplePayHelpers.h"
 #import "BUYClient.h"
 #import "BUYError.h"
+#import "BUYModelManagerProtocol.h"
+#import "BUYObjectProtocol.h"
+#import "BUYObserver.h"
 
 #import "BUYPaymentButton.h"
 #import "BUYProductViewController.h"