OC基础_字典

1.创建不可变字典对象

(1)NSDictionary *dic = [[NSDictionary alloc]init];

(2)NSDictionary *dic = [NSDictionary dictionary];

(3)NSDictionary *dic = [[NSDictionary alloc]initWithObjectsAndKeys:@"1", @"2", @"3", @"4",@"5", @"6", @"7", @"8", nil];

  NSLog(@"%@",dic);   //打印

     key 是唯一的,但是value可以重复

     key不为空

2. 当前有多少键值对 

 NSLog(@"%ld", dic.count); 

3.通过key找到对应value

      NSLog(@"%@", [dic objectForKey:@"2"]);         

        NSLog(@"%@", dic[@"2"]);  //dic[对应的key]

4.获取字典所有的key 和 value

 NSLog(@"%@", dic.allKeys);

        NSLog(@"%@", dic.allValues);

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1.创建可变的字典对象

NSMutableDictionary *dic = [NSMutableDictionary dictionary]; //定义空字典

NSMutableDictionary *dic1 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"1", @"2", @"3", @"4",@"5", @"6", nil];

2.for遍历该字典(遍历的是value)

for(NSInteger i = 0; i < dic1.allKeys.count; i++) {

       NSLog(@"%@", dic1.allValues[i]);

    }

    快速枚举遍历   

for (NSString *str in dic1) {

        NSLog(@"%@", str);          //遍历的是key

    }

    

       for (NSString *str in dic1) {

        NSLog(@"%@", dic1[str]);          //遍历的是value

       }

3.对可变的字典,当前key不存在的时候,是进行键值对的添加,当KEY存在,进行键值对的修改

NSMutableDictionary *dic = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"1", @"2", @"3", @"4",@"5", @"6", nil];

 对dic字典进行操作:

[dic setObject:@"7" forKey:@"8”]; //添加键值对

NSLog(@"%@", dic);

[dic setObject:@"7" forKey:@"8”]; //修改键值对

 NSLog(@"%@", dic);

 

       [dic removeObjectForKey:@"8”];   //移除键值对

       NSLog(@"%@", dic);

    

    [dic removeAllObjects];       //移除全部键值对

    NSLog(@"%@", dic);

4.字典里嵌套数组(两层)

NSArray *arr1 = @[@"1", @"2", @"3", @"4"];

      NSArray *arr2 = @[@"5", @"6", @"7", @"8"];

      NSMutableDictionary *dic = [NSMutableDictionary dictionaryWithObjectsAndKeys:arr1, @"arr1", arr2, @"arr2", nil];

  //遍历 放key的类型

      for(NSString *str in dic) {

      //针对对应的key找到value,value是一个数组,所以用一个数组对象来接受

       NSArray *arr = dic[str];

        for (NSString *temp in arr) {

          NSLog(@"%@", temp);

  }

      }

5.数组里嵌套字典(两层)

NSDictionary *dic1 = [NSDictionary dictionaryWithObjectsAndKeys:@"杨林", @"name", @"19", @"age", nil];

    NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"刘珊珊", @"name", @"14", @"age", nil];

    NSDictionary *dic3 = [NSDictionary dictionaryWithObjectsAndKeys:@"商帅", @"name", @"22", @"age", nil];

    NSArray *arr = @[dic1, dic2, dic3];

    //遍历value

    for (NSDictionary *dic in arr) {

        for (NSString *key in dic) {

            NSLog(@"%@", dic[key]);

        }

    }

6.三层嵌套

//字典嵌套数组,数组里再嵌套字典

NSDictionary *dic1 = [NSDictionary dictionaryWithObjectsAndKeys:@"杨林", @"name", @"19", @"age", nil];

 NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"刘珊珊", @"name", @"14", @"age", nil];

   NSDictionary *dic3 = [NSDictionary dictionaryWithObjectsAndKeys:@"商帅", @"name", @"22", @"age", nil];

   NSArray *arr1 = @[dic1, dic2];

    NSArray *arr2 = @[dic3];

    

    NSDictionary *bigDic = [NSDictionary dictionaryWithObjectsAndKeys:arr1,@"arr1", arr2, @"arr2", nil];

    

    for (NSString *str in bigDic) {

        NSArray *arr = bigDic[str]; //字典里嵌套数组,需要赋值

        //第二层

        for (NSDictionary *dic in arr) {

           //第三层

            for (NSString *temp in dic) {

                NSLog(@"%@",dic[temp]);

            }

        }

    }

//数组嵌套数组,再嵌套字典

    NSDictionary *dic1 = [NSDictionary dictionaryWithObjectsAndKeys:@"杨林", @"name", @"19", @"age", nil];

    NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"刘珊珊", @"name", @"14", @"age", nil];

    NSDictionary *dic3 = [NSDictionary dictionaryWithObjectsAndKeys:@"商帅", @"name", @"22", @"age", nil];

    NSArray *arr1 = @[dic1, dic2];

   NSArray *arr2 = @[dic3];

    

   NSArray *bigArr = @[arr1, arr2];

    for (NSArray *str in bigArr) { 

        for (NSDictionary *dic in str) {

            for (NSString *temp in dic ) {

                NSLog(@"%@", dic[temp]);

            }

        }

    }

7.字面量方式创建字典

NSDictionary *dic = @{@"1": @"2", @"3": @"4"};

NSLog(@"%@", dic);

例题:

   //定义三个书的字典

   NSMutableDictionary *book1 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"三国演义",@"name",@"100", @"price", nil];

    NSMutableDictionary *book2 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"水浒传",@"name",@"34", @"price", nil];

    NSMutableDictionary *book3 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"西游记",@"name",@"89", @"price", nil];

  //放在可变的数组里

    NSMutableArray *bookArr = [NSMutableArray arrayWithObjects:book1 ,book2, book3,nil];

  //添加,删除书籍

    NSMutableDictionary *book4 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"哈利波特",@"name",@"59", @"price", nil];

    

    [bookArr addObject:book4];

    NSLog(@"%@ %@", book4[@"name"], book4[@"price"]);

  //可以从数组根据书名查找书籍,并修改书籍的价格

    for (NSMutableDictionary *dic in bookArr) {

        if ([dic[@"name"]isEqualToString:@"三国演义"] ) {

            [dic setObject:@"1000" forKey:@"price"];

        }

    }

  //展示所有书籍清单

    for (NSMutableDictionary *dic in bookArr) {

        NSLog(@"%@", dic[@"name"]);

    }

注意区别:

NSMutableDictionary *dic = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"1", @"2", @"3", @"4",@"5", @"6", nil];

[dic setValue:nil forKey:@"2"]; //清空2所对应的键值对

NSLog(@"%@", dic);

[dic setObject:nil forKey:@"2"]; //错误:setObject后不可以为空

  NSLog(@"%@", dic);