指针和引用传递的区别 pointer和reference有什么差别 (转载)
原文链接:http://www.cnblogs.com/oomusou/archive/2006/10/22/536184.html
C语言和其它程序性语言,如FORTRAN,Pascal,BASIC最大的差别就在于pointer,而pointer也是学习C语言最大的门坎,pointer的本意是希望function在传递数据时,不用将数据用copy的方式将数据copy进function的stack中,以加快程序执行速度和节省内存,如array通常占的内存都很大,若copy的方式势必降低速度且耗内存,但pointer的缺点就是程序不易阅读,需要一段时间去熟析这种怪异的语法。
C++为了解决pointer程序不易阅读的问题,增加了reference型别,C#/Java也取消了pointer,用reference取代pointer,但reference和pointer有什么不同呢?
Reference基本上存的也是『内存地址』,这和pointer一样,但pointer取值时,还必须dereference,也就是必须透过『*』才能取值,因此才会出现*** pointer to pointer to pointer这种难以理解的语法,但reference是一种『高级的pointer』,不需deference即可取值,所以不论是几层,仍然是reference这个变量而已,也因为不需dereference,所以书上都强调reference可视为变量的alias(别名、化名)(C++ Primer 4th P.59 A reference is an alias.),这使的reference骨子里存的是内存地址,但用起来却和一般变量一样方便,程序也漂亮许多,我们看一下(以下程序摘自 多型与虚拟 对象导向的精随 P.27侯俊杰)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
3
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
4
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
5
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
6
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
7
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
8
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
9
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
10
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
11
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
12
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
13
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
14
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
15
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
16
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
17
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
18
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
19
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
20
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
21
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
22
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
23
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
24
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
25
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
26
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
各位就可看到,若用reference写,程序是不是好看很多了?再举一个例子,将两个变量的内容交换:
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
3
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
4
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
5
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
6
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
7
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
8
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
9
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
10
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
11
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
12
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
13
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
14
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
15
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
16
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
17
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
18
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
19
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
20
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
21
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
22
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
23
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
24
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
25
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
26
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
27
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
28
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
29
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
30
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
31
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
32
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
以上的例子,都明显的发现reference的确比pointer优秀,但相信很多人跟我一样,基乎没有使用这种Call by pointer(reference)的方式传值,都使用Call by value的方式,因为怕的就是Side effect,由于argument和parameter的内存地址相同,若function中不小心改了parameter的变量,就造成argument变量值改变了,在其它语言的确没有解决的方案(C#/Java/VB),但在C++中,提供了const reference的方式,让parameter为只读,若程序不小心改了parameter,compiler会挡下来:
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
3
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
4
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
5
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
6
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
7
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
8
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
9
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
10
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
11
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
12
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
13
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
14
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
15
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
16
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
17
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
18
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
19
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
20
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
21
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
所以为了程序效率以及节省内存,应该尽量使用reference来写程序,可以避免copy的动作,而且reference的写法程序的可读性远比pointer高,而写法基乎和一般变量一样,只有宣告reference时不一样而已。