NSDictionary *dic1=[NSDictionary dictionaryWithObjectsAndKeys: @"1",@"a",

                           @"2",@"b", @"3",@"c", @"2",@"d", nil];

       NSLog(@"%zi",[dic1 count]); //结果:4

       NSLog(@"%@",[dic1 valueForKey:@"b"]);//根据键取得值,结果:2

       NSLog(@"%@",dic1[@"b"]);//还可以这样读取,结果:2

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

NSDictionary *dic1=[NSDictionary dictionaryWithObjectsAndKeys: @"1",@"a",

                           @"2",@"b", @"3",@"c", @"2",@"d", nil];

       NSLog(@"%zi",[dic1 count]); //结果:4

       NSLog(@"%@",[dic1 valueForKey:@"b"]);//根据键取得值,结果:2

       NSLog(@"%@",dic1[@"b"]);//还可以这样读取,结果:2

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

       

       NSLog(@"%@",[dic1 objectsForKeys:[NSArray arrayWithObjects:@"a",@"b",@"e","r", nil]notFoundMarker:@"not found"]);//后面一个参数notFoundMarker是如果找不到对应的key用

NSMutableDictionary *dic=[NSMutableDictionary

                                 dictionaryWithObjectsAndKeys:@"1",@"a", @"2",@"b", @"3",@"c", @"2",@"d",nil];

       //[dic removeObjectForKey:@"b"];

       //NSLog(@"%@",dic);

       /*结果:

                          {

                          a = 1;

                          c = 3;

                          d = 2; }

                          */

       //[dic addEntriesFromDictionary:@{@"e":@"7",@"f":@"6"}];

       //NSLog(@"%@",dic);

       /*结果:

        {

        a = 1;

        c = 3; d = 2; e = 7; f = 6;

        } */

       //setValue:value forkey:key 如果key存在，修改value；否则添加

       [dic setValue:@"5" forKey:@"a"];

       [dic setValue:@"5" forKey:@"f"];

       NSLog(@"%@",dic);