设计模式之策略设计模式-白红宇

问题引入:在一些购物系统,可能会在搞一些促销，比如满多少减多少,全场打折等,那这样的怎么设计比较好呢？这时策略模式就是一个很好的解决方法。

1.定义

定义了一系列的算法，并将每一个算法封装起来，而且使它们还可以相互替换。策略模式让算法独立于使用它的客户而独立变化。

2.UML类图

3.实现

1、定义baseStrategy接口CashBase

#import 
    
     #import 
     
      @protocol CashBase 
      
       -(CGFloat)acceptCash:(CGFloat)cash;@end

2.定义Strategy接口子类CashNormal

#import 
    
     #import "CashBase.h"@interface CashNormal : NSObject
     
      @end

#import "CashNormal.h"@implementation CashNormal-(CGFloat)acceptCash:(CGFloat)cash{    return cash;}@end

定义子类CashRobate

#import 
    
     #import "CashBase.h"@interface CashRobate : NSObject
     
      -(instancetype)initWithMoneyRebate:(CGFloat)moneyRebate;@end

#import "CashRobate.h"@interface CashRobate ()@property(nonatomic)CGFloat moneyRebate;@end@implementation CashRobate-(instancetype)initWithMoneyRebate:(CGFloat)moneyRebate{    self = [super init];    if (self) {        _moneyRebate = moneyRebate;    }    return self;}-(CGFloat)acceptCash:(CGFloat)cash{    return self.moneyRebate * cash;}@end

定义子类CaseReturn

#import 
    
     #import "CashBase.h"@interface CaseReturn : NSObject
     
      -(instancetype)initWithMoneyCondition:(CGFloat)moneyCondition moneyReturn:(CGFloat)moneyReturn;@end

#import "CaseReturn.h"@interface CaseReturn ()@property(nonatomic)CGFloat moneyCondition;@property(nonatomic)CGFloat moneyReturn;@end@implementation CaseReturn-(instancetype)initWithMoneyCondition:(CGFloat)moneyCondition moneyReturn:(CGFloat)moneyReturn{    self = [super init];    if (self) {        _moneyCondition = moneyCondition;        _moneyReturn = moneyReturn;    }    return self;}-(CGFloat)acceptCash:(CGFloat)cash{    return self.moneyCondition - self.moneyReturn;}@end

定义context

#import 
    
     #import "CashBase.h"@interface CashContext : NSObject-(instancetype)initWithCashSuper:(id
     
      )cashBase;-(CGFloat)getResult:(CGFloat)money;@end

#import "CashContext.h"@interface CashContext()@property(strong,nonatomic) id
    
      cashSuper;@end@implementation CashContext-(instancetype)initWithCashSuper:(id
     
      )cashBase{    self = [super init];    if (self) {        self.cashSuper = cashBase;    }    return self;}-(CGFloat)getResult:(CGFloat)money{    return [self.cashSuper acceptCash:money];}@end

4.调用

CashRobate *robate = [[CashRobate alloc]initWithMoneyRebate:0.8];    CashContext *context = [[CashContext alloc]initWithCashSuper:robate];    NSLog(@"结果是%f",[context getResult:100]);        CaseReturn *cashReturn = [[CaseReturn alloc]initWithMoneyCondition:300 moneyReturn:100];    CashContext *contextReturn = [[CashContext alloc]initWithCashSuper:cashReturn];    NSLog(@"结果是%f",[contextReturn getResult:0]);

5.输出