集合

        /*
         NSSet是无序的
         NSSet中不能存储重复的数据，可以o用来去除重复的值
         */
        NSSet * set = [[NSSet alloc]initWithObjects:@"a",@"b",@"c", nil];
        NSLog(@"set中的值为%@",set);
        
        //NSSet的长度
        NSLog(@"set的长度是：%ld",set.count);
        
        //NSSet是否包含某个值
        if([set containsObject:@"b"]){
            NSLog(@"包含b");
        }else{
            NSLog(@"不包含b");
        }
        
        //遍历
        NSArray * array = [set allObjects];
        for (int i = 0; i<array.count; i++) {
            NSLog(@"value = %@",array[i] );
        }
       NSEnumerator * enumerator = [set objectEnumerator];
        id value;
        while (value = [enumerator nextObject]) {
            NSLog(@"value = %@",value);
        }

    //可变集合
    //创建一个可变集合
    NSMutableSet * mutableSet = [[NSMutableSet alloc]initWithCapacity:0];
    
    //添加数据
    [mutableSet addObject:@"one"];
    [mutableSet addObject:@"two"];
    NSLog(@"mutableSet值为：%@",mutableSet);
    
    //遍历数据
    NSEnumerator * enumerator2 = [mutableSet objectEnumerator];
    NSString * value2;
    while (value2 = [enumerator2 nextObject]) {
        NSLog(@"mutableSet值分别为：%@",value2);
    }
    
    //删除数据
    [mutableSet removeObject:@"one"];
    NSLog(@"mutableSet值为：%@",mutableSet);

    //删除所有元素
    [mutableSet removeAllObjects];
    NSLog(@"mutableSet值为：%@",mutableSet);

    /*
     集合之间的转换
     */
    //NSArray -> NSMutableArray
    NSArray * nsNrray = @[@"a",@"b",@"c"];
    NSMutableArray * nsMutableArray = [NSMutableArray arrayWithArray:nsNrray];
    NSLog(@"NSArray -> NSMutableArray : %@",nsMutableArray);
    
    //NSDictionary -> NSMutableDictionary
    NSDictionary * dictionary = @{@"one":[NSNumber numberWithInt:1],@"two":[NSNumber numberWithInt:2]};
    NSMutableDictionary * mutableDic = [NSMutableDictionary dictionaryWithDictionary:dictionary];
    NSLog(@"NSDictionary -> NSMutableDictionary : %@",mutableDic);
    
    //NSSet -> NSMutableSet
    NSSet * nsSet = [[NSSet alloc]initWithObjects:@"a",@"b", nil];
    NSMutableSet * nsMutableSet = [NSMutableSet setWithSet:nsSet];
    NSLog(@"NSSet -> NSMutableSet : %@",nsMutableSet);
    
    //NSArray -> NSSet
    NSLog(@"NSArray -> NSSet %@",[NSSet setWithArray:nsNrray]);
    
    //NSDictionary -> NSArray
    NSLog(@"NSDictionary ->key的 NSArray %@",[dictionary allKeys]);
    NSLog(@"NSDictionary ->value的 NSArray %@",[dictionary allValues]);
    
    //NSString -> NSArray
    NSString * str = @"www.baidu.com";
    NSLog(@"NSString -> NSArray : %@",[str componentsSeparatedByString:@"."]);