NSSet和NSMutableSet

        //NSArray 自然顺序
        //NSSet是无序的
        //注意:这个是最为重要的功能 NSSet中不能够存储重复的数据,可以用它来去除重复的值
        NSString * str1 = @"one";
        NSString * str2 = @"two";
        NSString * str3 = @"three";
        NSSet * set = [[NSSet alloc] initWithObjects:str1,str2,str3,str1, nil];
        NSLog(@"set %@",set);

        //count
        NSLog(@"count %ld",set.count);

       BOOL isContains =  [set containsObject:str1];
        if (isContains)
        {
            NSLog(@"YES");
        }
        else
        {
            NSLog(@"NO");
        }

        //4.遍历

        NSEnumerator * enumerator = [set objectEnumerator];
        NSString * value;
        while (value = [enumerator nextObject]) {
            NSLog(@"value %@",value);
        }

NSString * str1 = @"one";
        NSString * str2 = @"two";

        //1 创建一个可变集合
        NSMutableSet * muSet = [[NSMutableSet alloc] init];

        //2.增加值
        [muSet addObject:str1];
        [muSet addObject:str2];

        NSLog(@"muSet %@",muSet);

        //3.删除
        [muSet removeObject:str1];

        NSLog(@"muSet %@",muSet);

        //4.删除所有
//        [muSet removeAllObjects];

        NSLog(@"muSet %@",muSet);

        //5.遍历
        NSEnumerator * en = [muSet objectEnumerator];
        NSString * value;
        while (value = [en nextObject]) {
            NSLog(@"value %@",value);
        }