简单工厂学习的小例子

简单工厂模式（Simple Factory Pattern）属于类的创新型模式，又叫静态工厂方法模式（Static FactoryMethod Pattern）,是经过专门定义一个类来负责建立其余类的实例，被建立的实例一般都具备共同的父类。

下面的例子是一个实现基本四则运算的计算器.

1.涉及的类目录

分别对应+,-,*,/和一个工厂类

 

2.实现的细节

父类Operation

 1 #import <Foundation/Foundation.h>
 2 
 3 @interface Operation : NSObject
 4 @property (nonatomic,assign) float numA;
 5 @property (nonatomic,assign) float numB;
 6 - (float)result;
 7 @end
 8 
 9 
10 #import "Operation.h"
11 
12 @implementation Operation
13 - (float)result
14 {
15     return 0;
16 }
17 @end

有两个数和一个获取结果的方法

 

一下的类都是继承了Operation类,并重写了result方法

加.

#import "OperationAdd.h"

@implementation OperationAdd
- (float)result
{
    return self.numA + self.numB;
}
@end

　　减.

1 #import "OperationSub.h"
2 
3 @implementation OperationSub
4 - (float)result
5 {
6     return self.numA - self.numB;
7 }
8 @end

乘.

1 #import "OperationMul.h"
2 
3 @implementation OperationMul
4 - (float)result
5 {
6     return self.numA * self.numB;
7 }
8 @end

除

1 #import "OperationDiv.h"
2 
3 @implementation OperationDiv
4 - (float)result
5 {
6     NSAssert(0 != self.numB, @"除数不能为0");
7     return self.numA / self.numB;
8 }
9 @end

 

工厂类的实现

 1 #import "Operation.h"
 2 
 3 @interface OperationFactory : NSObject
 4 + (Operation*)createOperation:(char)symbol;
 5 @end
 6 
 7 #import "OperationFactory.h"
 8 #import "OperationAdd.h"
 9 #import "OperationSub.h"
10 #import "OperationMul.h"
11 #import "OperationDiv.h"
12 @implementation OperationFactory
13 + (Operation *)createOperation:(char)symbol
14 {
15     Operation *operation;
16     switch (symbol) {
17         case '+':
18             operation = [[OperationAdd alloc]init];
19             break;
20         case '-':
21             operation = [[OperationSub alloc]init];
22         case '*':
23             operation = [[Operation alloc]init];
24         case '/':
25             operation = [[OperationDiv alloc]init];
26         default:
27             break;
28     }
29     
30     return operation;
31 }
32 @end

主要是一个根据输入的运算操做符建立响应的运算计算结果的方法:

createOperation:

应用

 1 #import <Foundation/Foundation.h>
 2 #import "OperationFactory.h"
 3 int main(int argc, const char * argv[]) {
 4     @autoreleasepool {
 5         Operation *operation = [OperationFactory createOperation:'/' ];
 6         operation.numA = 10.0;
 7         operation.numB = 2;
 8     
 9         NSLog(@"div result = %f",[operation result]);
10         
11          operation = [OperationFactory createOperation:'+'];
12         operation.numA = 10.0;
13         operation.numB = 2;
14         NSLog(@"add result = %f",[operation result]);
15     
16     }
17     return 0;
18 }

结果

2016-01-18 09:25:38.778 FactoryModel[719:28322] div result = 5.000000

2016-01-18 09:25:38.779 FactoryModel[719:28322] add result = 12.000000