[Creational Pattern] Abstract factory pattern trong Objective C

Tiếp theo bài Singleton pattern. Bài này mình xin giới thiệu Abstract factory pattern trong nhóm Creational Pattern.

Khái niệm: Abstract factory pattern cung cấp một interface để tạo những mối quan hệ gia đình giữa những đối tượng liên quan hoặc phụ thuộc, không quy định chi tiết các lớp cụ thể của chúng.

Cấu trúc lớp: Hiện tại theo mình thấy thì có 2 cách để thể hiện Abstract factory như dùng interface hay dùng abstract class. Tuỳ theo cách dùng sẽ có cách vẽ sơ đồ lớp khác nhau.
- Trường hợp dùng Interface làm abstract factory sẽ có sơ đồ như sau:

- Trường hợp dùng Abstract Class làm abstract factory sẽ có sơ đồ như sau:

Cách sử dụng: Lớp client chỉ cần quan tâm đến những abstract factory mà không cần quan tâm đến những lớp cụ thể như productA1, productA2, productB1, productB2. Sơ đồ như sau:

Code ví dụ trong Objective C: Ví dụ mình dùng interface để thể hiện pattern này.
- Sơ đồ ví dụ như bên dưới:

Source from Wikipedia

- Code về những factory, cách viết interface trong objective C sử dụng protocol như sau:

	//GUIFactory.h
	#import <Foundation/Foundation.h>
	#import "Button.h"
	#import "Label.h"
	//Abstract Factory
	@protocol GUIFactory <NSObject>
	- (id<Button>)createButton;
	- (id<Label>)createLabel;
	@end

view raw objC_abstractFactory hosted with ❤ by GitHub

	//WinFactory.h
	#import <Foundation/Foundation.h>
	#import "GUIFactory.h"
	//Concrete Factory 1
	@interface WinFactory : NSObject <GUIFactory>
	@end

view raw objC_concreteFactory1_h hosted with ❤ by GitHub

	//WinFactory.m
	#import "WinFactory.h"
	#import "WinButton.h"
	#import "WinLabel.h"
	@implementation WinFactory
	- (id<Button>)createButton {
	return [[WinButton alloc] init];
	}
	- (id<Label>)createLabel {
	return [[WinLabel alloc] init];
	}
	@end

view raw objC_concreteFactory1_m hosted with ❤ by GitHub

	//OSXFactory.h
	#import <Foundation/Foundation.h>
	#import "GUIFactory.h"
	//Concrete Factory 2
	@interface OSXFactory : NSObject <GUIFactory>
	@end

view raw objC_concreteFactory2_h hosted with ❤ by GitHub

	//OSXFactory.m
	#import "OSXFactory.h"
	#import "OSXButton.h"
	#import "OSXLabel.h"
	@implementation OSXFactory
	- (id<Button>)createButton {
	return [[OSXButton alloc] init];
	}
	- (id<Label>)createLabel {
	return [[OSXLabel alloc] init];
	}
	@end

view raw objC_concreteFactory2_m hosted with ❤ by GitHub

- Code về những product như sau:

	//Button.h
	#import <Foundation/Foundation.h>
	//Abstract Product A
	@protocol Button <NSObject>
	- (NSString*)paint;
	@end

view raw objC_abstractProductA hosted with ❤ by GitHub

	//Label.h
	#import <Foundation/Foundation.h>
	//Abstract Product B
	@protocol Label <NSObject>
	- (NSString*)paint;
	@end

view raw objC_abstractProductB hosted with ❤ by GitHub

	//"WinButton.h"
	#import <Foundation/Foundation.h>
	#import "Button.h"
	//Concrete Product A1
	@interface WinButton : NSObject <Button>
	@end

view raw objC_concreteProductA1_h hosted with ❤ by GitHub

	//"WinButton.m"
	#import "WinButton.h"
	@implementation WinButton
	- (NSString*)paint {
	return @"WinButton";
	}
	@end

view raw objC_concreteProductA1_m hosted with ❤ by GitHub

	//"OSXButton.h"
	#import <Foundation/Foundation.h>
	#import "Button.h"
	//Concrete Product A2
	@interface OSXButton : NSObject <Button>
	@end

view raw objC_concreteProductA2_h hosted with ❤ by GitHub

	//"OSXButton.m"
	#import "OSXButton.h"
	@implementation OSXButton
	- (NSString*)paint {
	return @"OSXButton";
	}
	@end

view raw objC_concreteProductA2_m hosted with ❤ by GitHub

	//"WinLabel.h"
	#import <Foundation/Foundation.h>
	#import "Label.h"
	//Concrete Product B1
	@interface WinLabel : NSObject <Label>
	@end

view raw objC_concreteProductB1_h hosted with ❤ by GitHub

	//"WinLabel.m"
	#import "WinLabel.h"
	@implementation WinLabel
	- (NSString*)paint {
	return @"WinLabel";
	}
	@end

view raw objC_concreteProductB1_m hosted with ❤ by GitHub

	//"OSXLabel.h"
	#import <Foundation/Foundation.h>
	#import "Label.h"
	//Concrete Product B2
	@interface OSXLabel : NSObject <Label>
	@end

view raw objC_concreteProductB2_h hosted with ❤ by GitHub

	//"OSXLabel.m"
	#import "OSXLabel.h"
	@implementation OSXLabel
	- (NSString*)paint {
	return @"OSXLabel";
	}
	@end

view raw objC_concreteProductB2_m hosted with ❤ by GitHub

- Client gọi factory như sau:

	//Client.h
	#import "GUIFactory.h"
	#import "OSXFactory.h"
	#import "WinFactory.h"
	@interface Application : NSObject {
	}
	@property (nonatomic, strong) NSString* buttonAction;
	@property (nonatomic, strong) NSString* labelAction;
	- (instancetype)initWithFactory:(id<GUIFactory>)factory;
	@end

view raw objC_abstractFactoryClient_h hosted with ❤ by GitHub

	//"Client.m"
	@implementation Application
	- (instancetype)initWithFactory:(id<GUIFactory>)factory {
	self = [self init];
	if (self) {
	id<Button> button = [factory createButton];
	id<Label> label = [factory createLabel];
	_buttonAction = [button paint];
	_labelAction = [label paint];
	NSLog(@"Button action:%@ - Label action:%@",_buttonAction,_labelAction);
	}
	return self;
	}
	@end

view raw objC_abstractFactoryClient_m hosted with ❤ by GitHub

- Unit test cho pattern này:

	#import <XCTest/XCTest.h>
	#import "GUIFactory.h"
	#import "Application.h"
	/**
	* Todo list:
	* - Test win os, should return true, when create win object.
	* - Test osx, should return true, when create osx object.
	*/
	@interface AbstractFactoryTests : XCTestCase
	@end
	@implementation AbstractFactoryTests
	- (void)setUp {
	[super setUp];
	}
	- (void)tearDown {
	[super tearDown];
	}
	//Helper
	- (id<GUIFactory>)createSpecificOSWithEnvironment:(NSString*)environment {
	if ([environment isEqualToString:@"osx"]) {
	return [[OSXFactory alloc] init];
	}
	else if ([environment isEqualToString:@"win"]) {
	return [[WinFactory alloc] init];
	}
	return nil;
	}
	- (void)testRunWinOS {
	//GIVEN
	NSString* inputedValue = @"win";
	NSString* expectedValue1 = @"WinButton";
	NSString* expectedValue2 = @"WinLabel";
	//WHEN
	Application* app = [[Application alloc] initWithFactory:[self createSpecificOSWithEnvironment:inputedValue]];
	//THEN
	XCTAssertEqualObjects(expectedValue1, app.buttonAction);
	XCTAssertEqualObjects(expectedValue2, app.labelAction);
	}
	- (void)testRunOSX {
	//GIVEN
	NSString* inputedValue = @"osx";
	NSString* expectedValue1 = @"OSXButton";
	NSString* expectedValue2 = @"OSXLabel";
	//WHEN
	Application* app = [[Application alloc] initWithFactory:[self createSpecificOSWithEnvironment:inputedValue]];
	//THEN
	XCTAssertEqualObjects(expectedValue1, app.buttonAction);
	XCTAssertEqualObjects(expectedValue2, app.labelAction);
	}

view raw objC_abstractFactoryTests hosted with ❤ by GitHub

Tài liệu tham khảo:

- Wikipedia

- Stackoverflow