OC学习笔记 Foundation 集合类 字典Dictionary

字典 由键-值对组成的数据集合

4种创建字典方式

1>针对单个键值对 直接赋值

 1  NSDictionary *dic = [NSDictionary dictionaryWithObject:@"dajie" forKey:@"name"];//直接创建字典
 2     id object = [dic objectForKey:@"name"];// 取出name键对应值
 3     NSLog(@"%@",object);

2>以键值对集合创建

      NSArray *obj = @[@"dajie",@"ly"];
      NSArray *keys = @[@"name",@"address"];
      NSDictionary *dic1 = [NSDictionary dictionaryWithObjects:obj forKeys:keys];//创建字典
      NSLog(@"%@",dic1);

3>直接创建并赋值

     NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"dajie",@"name",@"ly",@"address", nil];//nil不可少
     NSLog(@"
---%@",dic2);

3      id obj2 = [dic2 objectForKey:@"name"];//根据键取出对应的值
4      NSLog(@"%@",obj2);

4>开发中常用

　　　　//xcode 新特性 开发中常用
15     NSDictionary *dic3 = @{@"name" : @"dajie",@"address":@"ly",@"qq":@"12324124"};
16     NSLog(@"%@
--%@--%ld",dic3,[dic3 objectForKey:@"name"],dic3.count);

可变字典

     NSMutableDictionary *mdic = [NSMutableDictionary dictionary];//创建

添加元素和删除元素

//添加键值对
20     [mdic setObject:@"dajie" forKey:@"person"];
21     [mdic setObject:@"hashiqi" forKey:@"dog"];
22     [mdic setObject:@"shapi" forKey:@"dog"];  //主键一样字典元素前者会被后者覆盖
23     NSString *str = mdic[@"dog"];
24     NSLog(@"%@",str);
25   //删除
26     [mdic removeAllObjects];
27     [mdic removeObjectForKey:@"dog"];
28     NSLog(@"%@",mdic);

遍历元素

1基本for循环遍历

30  　　NSDictionary *newDic = @{
31                              @"name": @"dajie",
32                              @"dog":@"HASHIQI"
　　　　};
33     NSArray *key = [newDic allKeys];//取出所有的key
34     for (int i;  i < newDic.count; i++) {
35         NSString *keys = key[i];
36         NSString *value = newDic[keys];
37         NSLog(@"%@ = %@",keys,value);
38     }

2 简洁遍历

//推荐使用 快速遍历
40     [newDic enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
41         NSLog(@"%@ - %@ ",key ,obj );
42     }];

 总结

/* NSArray 相当于java List;
// NSSet相当于java Set 
// NSdictionary相当于java Map 
// NSArray NSMutableArray
有序 快速访问 @[obj1,obj2,obj3];
快速访问元素 数组名[i];

// NSSet NSMutableSet
无序
// NSDictionary NSMutableDictionary 
无序 快速创建@{key1 : value1,key2 : value2};
快速访问 字典名[key];
*/

    NSArray *persons = @[
@{@"name" :@"dajie",@"phone":@"1234353",
  @"books" : @[@"5分钟编程ios",@"5分钟编程Android"]},
@{@"name" :@"xiaojie",@"phone":@"2234353"},
  @{@"name" :@"jinyu",@"phone":@"3234353",@"age" : @"1.2"}
                         ];
    // 先取出数组位置对应的字典
    // 再根据字典name这个key找到对应的值
//    NSLog(@"%@",persons[1][@"name"]);
//      NSLog(@"%@",persons[0][@"books"]);
    
    for (NSString *arrays in persons) {
//     NSInteger *lines  = [persons indexOfObject:@"name"];
//        NSLog(@"%ld - %@",lines,arrays);
        NSLog(@" %@ ",arrays);
    }