OC中的NSValue

 1     NSvalue把複雜的數據類型（指針、結構體等）存儲成對象
 2     
 3     struct sct{
 4         int a;
 5         int b;
 6     }sctt={4,5};  
 7     
 8     NSValue *value=[[NSValue alloc] initWithBytes:&sctt objCType:@encode(struct sct)];
 9     
10     NSLog(@"%s",@encode(int));結果是i
11     NSLog(@"%s",@encode(float));結果是f
12     NSLog(@"%s",@encode(long));結果是q
13     NSLog(@"%s",@encode(struct sct));結果是{sct=ii}
14     //同過每個類型生成的字符串是惟一的
15     if(strcmp(value.objCType, @encode(struct sct))==0{
16         NSLog(@"it is struct sct");
17     }
18     
19     //取出結構體數據
20     struct sct newSctt;
21     [value getValue:&newSctt];
22     NSLog(@"%d %d",newSctt.a,newSctt.b);//結果是 4 5
23     [value release];
24     
25     
26     
27     char *p=(char *)0x1f;
28     NSValue *value1=[[NSValue alloc] initWithBytes:&p objCType:@encode(char *)];
29     
30     char *q;
31     [value1 getValue:&q];
32     NSLog(@"%p",q);結果是0x1f
33     [value1 release];
34     
35     
36     CGPoint point;
37     CGsize size;
38     CGRect rect;
39     NSValue *pointValue=[NSValue valueWithPoint:point];
40     NSValue *sizeValue=[NSValue valueWithSize:size];
41     NSvalue *recrValue=[NSValue valueWithRect:rect];
42     NSValue & rangeValue=[NSValue valueWithRange:NSMakeRange(3,4)];