簡單工廠模式
正如此模式的名稱一樣，簡單工廠模式基本上是所有設計模式里最簡單的一種，類與類之間的關系一目了然。這次我就用很多地方經常舉的例子－－計算器，來說明這個模式。首先給大家展示一下類之間的結構圖：
通過這張結構圖，可以清晰的看到，加法類、減法類、乘法類、除法類繼承自運算類，簡單工廠類依賴于運算類的實例化來實現相應的運算功能，好的，看起來并不復雜，讓我們直接展示一下代碼吧(鑒于目前點點不支持Objective C的代碼高亮，所以就直接寫啦，盡量保持整齊吧。另，為了照顧像我一樣基礎不是很好的同學，我盡量把代碼寫全，方便大家調試)。
注意：本文所有代碼均在ARC環境下編譯通過。
首先是運算類（父類）：
接口文件：
#import <Foundation/Foundation.h>
@interface Operation :NSObject{
double numberA;
double numberB;
}
@property double numberA;
@property double numberB;
-(double) GetResult;
@end
實現文件：
#import"Operation.h"
@implementation Operation
@synthesize numberA, numberB;
-(double) GetResult{
return -1.0; //此處默認返回-1.0，無其他意義
}
@end
加法類（運算子類）：
接口文件：
#import "Operation.h"
@interface OperationAdd:Operation
@end
實現文件：
#import "OperationAdd.h"
@implementation OperationAdd
-(double) GetResult{
double result =0;
result =numberA+numberB;
return result;
}
@end
減法類（運算子類）：
接口文件：
#import "Operation.h"
@interface OperationSub:Operation
@end
實現文件：
#import "OperationSub.h"
@implementation OperationSub
-(double)GetResult{
double result =0;
result = numberA-numberB;
return result;
}
@end
乘法類（運算子類）
#import "Operation.h"
@interface OperationMul:Operation
@end
實現文件：
#import "OperationMul.h"
@implementation OperationMul
-(double)GetResult{
double result =0;
result = numberA*numberB;
return result;
}
@end
除法類（運算子類）：
接口文件：
#import "Operation.h"
@interface OperationDiv:Operation
@end
實現文件：
#import "OperationDiv.h"
@implementation OperationDiv
-(double)GetResult{
double result =0;
@try{
result = numberA/numberB;
}
@catch(NSException *exception) {
NSLog(@"除數不能為0");
}
return result;
}
@end
下面是工廠類（依賴實力化運算類實現具體功能）：
接口文件：
#import <Foundation/Foundation.h>
#import "OperationAdd.h"
#import "OperationDiv.h"
#import "OperationSub.h"
#import "OperationMul.h"
@interface OperationFactory:NSObject
+(Operation*)CreateOperate:(char)operate;
@end
實現文件：
#import "OperationFactory.h"
+(Operation*)CreateOperate:(char)operate{
Operation *oper;
switch(operate) {
case '+':
oper = [[OperationAdd alloc]init];
break;
case '-':
oper = [[OperationSub alloc]init];
break;
case '*':
oper = [[OperationMul alloc]init];
break;
case '/':
oper = [[OperationDiv alloc]init];
break;
default:
oper = nil;
break;
}
return oper;
}
具體調用
#import <Foundation/Foundation.h>
#import "OperationAdd.h"
#import "OperationDiv.h"
#import "OperationMul.h"
#import "OperationSub.h"
#import "OperationFactory.h"
int main (int argc,const char* argv[])
{
@autoreleasepool{
Operation *oper = [OperationFactory CreateOperate:'*'];
[oper setNumberA:1];
[oper setNumberB:2];
double result = 0;
result = [oper GetResult];
NSLog(@"Result is %f", result);
}
return 0;
}
好啦，上面羅列的是簡單工廠模式的基礎代碼。其實還是挺簡單的，對吧，只有一層繼承關系，一個依賴關系，在工廠類里面用switch語句判別需要實例化哪種類型，之后進行計算，獲取結果。
工廠方法模式
上面關于簡單工廠模式中就有提到過一次關于“工廠類”模式。為了幫助大家能夠回憶一下簡單工廠模式，在這里提一下簡單工廠模式的優點，簡單工廠模式的最大優點在于工廠類中包含了必要的邏輯判斷，根據客戶端的選擇條件動態實例化相關的類，對于客戶端來說，去除了與具體產品的依賴。其實，工廠方法模式是簡單工廠模式的進一步抽象和推廣。由于使用了多態性，工廠方法模式保持了簡單工廠模式的優點，而且克服了它的缺點。但缺點是，由于每加一個產品，就需要加一個產品工廠的類，增加了額外的開發量。
下面還是以計算器為例子，詳細介紹工廠方法模式，還是老樣子，先向大家展示一下類結構圖。
上面這張圖向大家展示了各個類之間的關系。其實和簡單工廠模式不同的是，類圖的右邊抽象工廠接口是相比簡單工廠模式多出來的抽象接口。
下面直接上代碼吧，別的不多說了。
注意：本文所有代碼均在ARC環境下編譯通過。
Operation類接口
#import <Foundation/Foundation.h>
@interface Operation :NSObject{
double numberA;
double numberB;
}
@property double numberA;
@property double numberB;
-(double) GetResult;
@end
Operation類實現
#import "Operation.h"
@implementation Operation
@synthesize numberA, numberB;
-(double) GetResult{
return -1.0;
}
@end
OperationAdd類接口
#import "Operation.h"
@interface OperationAdd :Operation
@end
OperationAdd類實現
#import "OperationAdd.h"
@implementation OperationAdd
-(double) GetResult{
double result =0;
result = numberA+numberB;
return result;
}
@end
OperationDiv類接口
#import "Operation.h"
@interface OperationDiv :Operation
@end
OperationDiv類實現
#import "OperationDiv.h"
@implementation OperationDiv
-(double)GetResult{
double result =0;
@try{
result = numberA/numberB;
}
@catch(NSException *exception) {
NSLog(@"除數不能為0");
}
return result;
}
@end
OperationMul類接口
#import "Operation.h"
@interface OperationMul :Operation
@end
OperationMul類實現
#import "OperationMul.h"
@implementation OperationMul
-(double)GetResult{
double result =0;
result = numberA*numberB;
return result;
}
@end
OperationSub類接口
#import "Operation.h"
@interface OperationSub :Operation
@end
OperationSub類實現
#import "OperationSub.h"
@implementation OperationSub
-(double)GetResult{
double result =0;
result = numberA-numberB;
return result;
}
@end
IFactory類接口
#import <Foundation/Foundation.h>
#import "Operation.h"
@interface IFactory :NSObject
-(Operation*)CreateOperation;
@end
IFactory類實現
#import "IFactory.h"
@implementation IFactory
-(Operation*)CreateOperation{
return [[Operation alloc]init];
}
@end
AddFactory類接口
#import "IFactory.h"
@interface AddFactory :IFactory
@end
AddFactory類實現
#import "AddFactory.h"
#import "OperationAdd.h"
@implementation AddFactory
-(Operation*)CreateOperation{
return [[OperationAdd alloc]init];
}
@end
SubFactory類接口
#import "IFactory.h"
@interface SubFactory :IFactory
@end
SubFactory類實現
#import "SubFactory.h"
#import "OperationSub.h"
@implementation SubFactory
-(Operation*)CreateOperation{
return [[OperationSub alloc]init];
}
@end
MulFactory類接口
#import "IFactory.h"
@interface MulFactory :IFactory
@end
MulFactory類實現
#import "MulFactory.h"
#import "OperationMul.h"
@implementation MulFactory
-(Operation*)CreateOperation{
return [[OperationMul alloc]init];
}
@end
DivFactory類接口
#import "IFactory.h"
@interfaceDiv Factory :IFactory
@end
DivFactory類實現
#import "DivFactory.h"
#import "OperationDiv.h"
@implementation DivFactory
-(Operation*)CreateOperation{
return [[OperationDiv alloc]init];
}
@end
Main方法調用
#import <Foundation/Foundation.h>
#import "OperationAdd.h"
#import "AddFactory.h" //加法工廠,你可以根據需要添加其他運算工廠
int main (int argc,const char* argv[])
{
@autoreleasepool{
IFactory *operFactory = [[AddFactory alloc]init];
Operation *oper = [operFactory CreateOperation];
[oper setNumberA:1];
[oper setNumberB:2];
double result = [oper GetResult];
NSLog(@"The result is %f", result);
}
return 0;
}
好啦，上面就是工廠方法模式的Objective C的類代碼。
