关于objective-c函数参数怎么地址传递

- (void) doChange:(NSData *) data
{
    int length = [data length];
    int seed = 100;
    NSLog(@"%@",data);
    NSLog(@"data length:%i",length);
    Byte buffer[length];
    
    [data getBytes:buffer] ;
    
    int i;
    for(i=0;i<length;i++)
    {
        buffer[i] = (Byte)(buffer[i] ^ seed);
        seed++;
            //NSLog(@"%i",buffer[i]);
    }
    NSData * data2 = [NSData dataWithBytes:buffer length:length];
    NSLog(@"%@",data2);
    data = data2;
    NSLog(@"%@",data);
}

[self doChange:body];
NSLog(@"%@",body);

- (void) doChange:(NSData **) dataPoint//
{
    NSData* data = *dataPoint;//取值
    int length = [data length];
    int seed = 100;
    NSLog(@"%@",data);
    NSLog(@"data length:%i",length);
    Byte buffer[length];
    
    [data getBytes:buffer] ;
    
    int i;
    for(i=0;i<length;i++)
    {
        buffer[i] = (Byte)(buffer[i] ^ seed);
        seed++;
            //NSLog(@"%i",buffer[i]);
    }
    NSData * data2 = [NSData dataWithBytes:buffer length:length];
    [color=#FF0000]NSLog(@"%@",data2);
    *dataPoint = data2;//改变指针指向的值
    NSLog(@"%@",*dataPoint);[/color]
}

[self doChange:&body];//传入对象地址
NSLog(@"%@",body);

------解决方案--------------------
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引用:

引用:

你在C中，能直接这样“ data = data2;”地去改变指针的值吗


汗，data和data2都是指针，c里边当然是这么改变指针的值，data = data2表示把data和data2指向同一个对象，难道不对吗？