Foundation--NSDictionary+NSMutableDictionary

 键值对 key（一般为字符串对象）---vaule（必须是对象）

        Person *p1 =[[Person alloc ]init];

        Person *p2 =[[Person alloc ]init];

        Person *p3 =[[Person alloc ]init];

 

NSDictionary

创建一个字典

        NSDictionary *dic =@{@"p1":p1,@"p2":p2,@"p3":p3};

通过键访问值

        Person *p4 = [dic objectForKey:@"p1"];

遍历字典

        NSArray *allKeys = [dic allKeys];

        NSLog(@"allkey: %@",allKeys);

        NSArray *allValue = [dic allValues];

        NSLog(@"allValue: %@",allValue); 

        for (NSString * key in allKeys) {

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

        }

获取键值对个数

        NSLog(@"%ld",dic.count);

        

NSMutableDictionary              

创建可变字典

        NSMutableDictionary * dic = [NSMutableDictionary dictionaryWithCapacity:0];

添加值

        [dic setObject:p1 forKey:@"p1"];

        [dic setObject:p2 forKey:@"p2"];

        [dic setObject:p3 forKey:@"p3"];

        NSArray *allKeys = [dic allKeys];

更改某一个值

        [dic setObject:p3 forKey:@"p1"];

删除某一个值

        [dic removeObjectForKey:@"p1"];

全部删除值

        [dic removeAllObjects];