image.png

那么用策略模式如何实现呢?也是一段非常简单的代码:

NSDictionary *dict =@{
                          @"类型1" : @001,
                          @"类型2" : @002,
                          @"类型3" : @003
                          };
    
    NSInteger id = dict[type];//type 为类型1,类型2,类型3

eg

周一打篮球
周二逛街
周三洗衣服
周四打游戏
周五唱歌
周六看电影
周末爬山

我们用分支来写,应该是这样的:

if(day == 周一){
      result = [xiaoming playBasketball];
    }else if (day == 周二){
      result =  [xiaoming shopping];
    }else if (day == 周三){
      result =  [xiaoming washClothes];
    }else if(...) {
        ...
    }//很烦,写不下去了
NSLog(@"xiaoming 今天%@",result);

用策略：

// 1.将复杂的业务逻辑包装成invocation,这里传入的每天做的事,例如playBasketball
- (NSInvocation *)invocationWithMethod:(SEL)selector{
    NSMethodSignature*signature = [CurrentClass instanceMethodSignatureForSelector:@selector(selector)];
    NSInvocation*invocation = [NSInvocation invocationWithMethodSignature:signature];
    invocation.target = self;
    invocation.selector = @selector(selector);
    return invocation;
}
// 2.将每天做的事进行整合
- (NSDictionary *)Strategies{
   NSDictionary *Strategies = @{
                           @"day1" : [self invocationWithMethod:@selector(playBasketball)],
                           @"day2" : [self invocationWithMethod:@selector(shopping)],
                           @"day3" : [self invocationWithMethod:@selector(washClothes)],
                           @"day4" : [self invocationWithMethod:@selector(playGames)],
                           @"day5" : [self invocationWithMethod:@selector(sing)],
                           @"day6" : [self invocationWithMethod:@selector(watchMovie)],
                           @"day7" : [self invocationWithMethod:@selector(climbing)],
                           };
   return Strategies;
}
// 3.找出小明哪天做的事
    NSInvocation *doWhat = self.Strategies[whichDay];
    [doWhat invoke];

eg：例子

image.png

//平时解答
- (BOOL)isValid:(NSString *)str{
    char array[64] ;
    NSInteger location = 0;
    NSInteger len = str.length;
    if(len < 1){
        return NO;
    }
    for (int  i = 0; i < len; i++) {
        char c = [str characterAtIndex:i];
        if(c == '(' || c == '{' || c == '['){
            array[location] = c;
            location ++;
        }else{
            if (location == 0 )return NO;
            char tmpLeft = array[location -1];
            if (tmpLeft == '(' && c != ')') return NO;
            if (tmpLeft == '{' && c != '}') return NO;
            if (tmpLeft == '[' && c != ']') return NO;
            location --;
        }
    }
    return location == 0 ? YES : NO;
}

用策略

- (BOOL)isValid2:(NSString *)str{
    char array[64] ;
    NSInteger location = 0;
    NSInteger len = str.length;
    
    NSDictionary *dict = @{@"(":@")",
                           @"{":@"}",
                           @"[":@"]"
                           };
    
    if(len < 1){
        return NO;
    }
    for (int  i = 0; i < len; i++) {
        char c = [str characterAtIndex:i];
        NSString *strTmp = [[NSString alloc] initWithCString:c];
        if([dict.allKeys containsObject:strTmp]){
            array[location] = c;
            location ++;
        }else{
            if (location == 0 )return NO;
            NSString * tmpLeft =  [[NSString alloc] initWithCString: array[location -1]];
            if ( strTmp != dict[tmpLeft]) return NO;
            location --;
        }
    }
    return location == 0 ? YES : NO;
}

知识拓展

1.if else的原li

2.switch case 原理

3. 字典的实现原理

4. 引用文章连接