[OC Foundation框架 - 10] NSDictionary

通过唯一的key找到相应的value，类似于Map

NSDictionary是不可变的

 

1.创建

 void dicCreate()
 {
     //Immutable
 //    NSDictionary *dic = [NSDictionary dictionary];

     NSDictionary *dic = [NSDictionary dictionaryWithObject:@"Simon" forKey:@"name"];

     dic = [NSDictionary dictionaryWithObjectsAndKeys:@"v1", @"k1", @"v2", @"k2", nil];

     NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil];
     NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];
     dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys];

     NSLog(@"%@", dic);

 }

 

集中批量创建字典

         NSDictionary *d11_1 = @{@"姓名":@"张三", @"年龄":@"", @"性别":@"男"};

 

若存在同名的元素，采用最先定义的，多余的元素不会被计数

不允许nil作为键值

NSMutableDictioinary不能使用此方法，因为返回的是一个NSDictionary

 

 

2.基本操作

（1）键值对数量

（2）比较

（3）取值

（4）IO操作

 void dicUse()
 {
     NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil];
     NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];
     NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys];

     NSLog(@"%@", [dic objectForKey:@"k1"]);
 }

 void dicUse2()
 {
     NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v1", @"v2", nil];
     NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];
     NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys];

     NSArray *keys2 = [dic allKeys];
     NSLog(@"%@", keys2);

     NSArray *keys3 = [dic allKeysForObject:@"v1"];
     NSLog(@"%@", keys3);

     NSArray *objs2 = [dic objectsForKeys:[NSArray arrayWithObjects:@"k1",@"k2",@"k4",nil] notFoundMarker:@"not found"];
     NSLog(@"%@", objs2);
 }

 

3.遍历

 void dicLoop()
 {
     NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil];
     NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];
     NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys];

     //Loop all keys in dictionary
     for (id key in dic)
     {
         id value = [dic objectForKey:key];
         NSLog(@"%@ = %@", key, value);
     }
 }

 

4.迭代器

 void dicEnumerator()
 {
     NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil];
     NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];
     NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys];

     //key enumerator
     NSEnumerator *enumerator = [dic keyEnumerator];
     id key =nil;
     while (key = [enumerator nextObject])
     {
         id value = [dic objectForKey:key];
         NSLog(@"%@ = %@", key, value);
     }
 }

 

5.block迭代

 void dicBlockLoop()
 {
     NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil];
     NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];
     NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys];

     [dic enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
         NSLog(@"%@ - %@", key, obj);
     }];
 }

 

6.内存管理

 void memoryManage()
 {
     Student *stu1 = [Student studentWithName:@"Simon"];
     Student *stu2 = [Student studentWithName:@"Joke"];
     Student *stu3 = [Student studentWithName:@"Man"];
     NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:stu1,@"stu1",
                                                                     stu2, @"stu2",
                                                                     stu3, @"stu3", nil];

      //When dictionary is destroyed, the keys & objects will be released one time
     NSLog(@"stu1 before dic release:%zi", stu1.retainCount);
 }

 

7.取出键、值

(1)

         NSArray *da = [d allKeys];

(2)

         NSLog(@"%@", d[@""]);

 

8.NSDictionary是无序的，取出来的值不会按照存入的顺序排列

         NSMutableDictionary *d = [NSMutableDictionary dictionary];
         for (int i=; i<; i++)
         {
             [d setObject:@"abc" forKey:[NSString stringWithFormat:@"%d", i]];
         }

         NSLog(@"%@", d);

 

out:

2014-11-19 02:36:25.850 03-NSArray[5171:303] {
    0 = abc;
    1 = abc;
    10 = abc;
    11 = abc;

...