OC中的NSValue

    NSvalue把复杂的数据类型（指针、结构体等）存储成对象
    
    struct sct{
        int a;
        int b;
    }sctt={4,5};  
    
    NSValue *value=[[NSValue alloc] initWithBytes:&sctt objCType:@encode(struct sct)];
    
    NSLog(@"%s",@encode(int));结果是i
    NSLog(@"%s",@encode(float));结果是f
    NSLog(@"%s",@encode(long));结果是q
    NSLog(@"%s",@encode(struct sct));结果是{sct=ii}
    //同过每一个类型生成的字符串是唯一的
    if(strcmp(value.objCType, @encode(struct sct))==0{
        NSLog(@"it is struct sct");
    }
    
    //取出结构体数据
    struct sct newSctt;
    [value getValue:&newSctt];
    NSLog(@"%d %d",newSctt.a,newSctt.b);//结果是 4 5
    [value release];
    
    
    
    char *p=(char *)0x1f;
    NSValue *value1=[[NSValue alloc] initWithBytes:&p objCType:@encode(char *)];
    
    char *q;
    [value1 getValue:&q];
    NSLog(@"%p",q);结果是0x1f
    [value1 release];
    
    
    CGPoint point;
    CGsize size;
    CGRect rect;
    NSValue *pointValue=[NSValue valueWithPoint:point];
    NSValue *sizeValue=[NSValue valueWithSize:size];
    NSvalue *recrValue=[NSValue valueWithRect:rect];
    NSValue & rangeValue=[NSValue valueWithRange:NSMakeRange(3,4)];