[OC Foundation框架

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":@"21", @"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[@"6"]);

 

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=0; i<100; 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;

...