基本概念
策略模式：定义了算法家族，分别封装起来，让他们之间可以互相替换，不会影响到使用算法的客户。
简单策略的实现：
（1）创建Strategy的基类，定义所有Strategy都要实现的相同的方法，定义所有支持的算法的公共接口，例如播放器有播放，停止等
@interface StragegyBaseObject : NSObject
- (void)tryStragegyLog;
- (void)play;
- (void)stop;
@end
#import "StragegyBaseObject.h"
@implementation StragegyBaseObject
@end
(2)创建两个类，分别继承StragegyBaseObject，实现所有的公用方法
#import "StragegyFirst.h"
@implementation StragegyFirst
- (void)tryStragegyLog
{
NSLog(@"StragegyFirst");
}
- (void)play
{
NSLog(@"StragegyFirst play");
}
- (void)stop
{
NSLog(@"StragegyFirst stop");
}
@end
#import "StagegySecond.h"
@implementation StagegySecond
- (void)tryStragegyLog
{
NSLog(@"StagegySecond");
}
- (void)play
{
NSLog(@"StagegySecond play");
}
- (void)stop
{
NSLog(@"StagegySecond stop");
}
@end
（3）创建context
#import <Foundation/Foundation.h>
#import "StragegyBaseObject.h"
typedef enum : NSUInteger {
StrategyContextTypeFirst,
StrategyContextTypeSecond,
} StrategyContextType;
@interface StrategyContext : NSObject
@property (nonatomic, strong)StragegyBaseObject *stragegy;
- (instancetype)initWithStrategyContextType:(StrategyContextType)type;
- (void)tryStragegyLog;
- (void)play;
- (void)stop;
@end
#import "StrategyContext.h"
#import "StragegyFirst.h"
#import "StagegySecond.h"
@implementation StrategyContext
- (instancetype)initWithStrategyContextType:(StrategyContextType)type
{
self = [super init];
if (self) {
switch (type) {
case StrategyContextTypeFirst:
{
self.stragegy = [[StragegyFirst alloc] init];
}
break;
case StrategyContextTypeSecond:
{
self.stragegy = [[StagegySecond alloc] init];
}
break;
default:
break;
}
}
return self;
}
- (void)tryStragegyLog
{
[self.stragegy tryStragegyLog];
}
- (void)play
{
[self.stragegy play];
}
- (void)stop
{
[self.stragegy stop];
}
@end
（4）最终调用
StrategyContext *context = [[StrategyContext alloc] initWithStrategyContextType:StrategyContextTypeSecond];
[context tryStragegyLog];
[context play];
环境(Context)角色：持有一个Strategy的引用;
抽象策略(Strategy)角色：这是一个抽象角色，通常由一个接口或抽象类实现。此角色给出所有的具体策略类所需的接口;
具体策略(ConcreteStrategy)角色：包装了相关的算法或行为;
