动态数组传递给函数 [英] Dynamic Arrays passing to functions

问题描述

我在主函数创建2动态数组。我已经按引用传递两者的功能。然后，我从较小的动态数组数据复制到更大的动态数组。我删除较小的动态数组。较大的动态数组的地址分配给较小的动态数组。现在最好的ARR数组应具有的10大小然而，当我尝试打印主数组的第6要素，它崩溃。请看看下面的code：

 的#include＆LT;＆iostream的GT;
＃包括LT＆;串GT;使用命名空间std;无效FUNC（字符串*改编，串* BRR）;诠释的main（）
{
    字符串* ARR =新的字符串[5];
    改编[0] =hello0;
    改编[1] =hello1;
    ARR [2] =hello2;
    改编[3] =hello3;
    改编[4] =hello4;    字符串* BRR =新的字符串[10];
    FUNC（ARR，BRR）;    的for（int i = 0;我6;;我++）
        COUT＆LT;＆LT;改编[1]  - ;＆下; ENDL;    返回0;
}无效FUNC（字符串*改编，串* BRR）
{
    的for（int i = 0;我小于5;我++）
        BRR [I] =改编[I]    对于（I = 0; I＆小于5;我+ +）
        COUT＆LT;＆LT; BRR [1]  - ;＆下; ENDL;    删除[] ARR;    ARR = BRR;    改编[5] =hello5;
}
 

解决方案

这行有呼叫者绝对没有任何影响：

 改编= BRR;
 

所以，通话结束后， 改编点究竟在何处使用点之前 - 到现在是无效的内存区域（因为你已经删除）

如果这将是一个C的问题，我会建议你用一个指针的指针（字符串**改编）。不过，我觉得这是一个C ++程序讨厌。也许你想的地方使用参考？

I have created 2 dynamic arrays in the main function. I have passed both of them to the function by reference. Then I copy data from smaller dynamic array to the larger dynamic array. I delete the smaller dynamic array. Assign the address of the larger dynamic array to the smaller dynamic array. Now ideally the arr array should have size of 10. However, when I try to print the 6th element of the array in the main, it crashes. Please have a look at the code below:

#include <iostream>
#include <string> 

using namespace std; 

void func(string * arr, string * brr); 

int main()             
{ 
    string* arr = new string[5]; 
    arr[0] = "hello0"; 
    arr[1] = "hello1"; 
    arr[2] = "hello2"; 
    arr[3] = "hello3"; 
    arr[4] = "hello4"; 

    string* brr = new string[10]; 


    func(arr, brr); 

    for(int i = 0; i < 6; i++) 
        cout << arr[i] << endl; 

    return 0; 
} 

void func(string * arr, string * brr) 
{ 
    for(int i = 0; i < 5; i++) 
        brr[i] = arr[i]; 

    for(i = 0; i < 5; i++) 
        cout << brr[i] << endl; 

    delete []arr; 

    arr = brr; 

    arr[5] = "hello5";
} 

解决方案

This line has absolutely no effect for the caller:

arr = brr;

So after the call, arr points exactly where it used to point before - to a now invalid memory area (because you deleted it).

If this would be a C question, I would advise you to use a pointer to a pointer (string **arr). However, I feel this is nasty in a C++ program. Maybe you want to use a reference somewhere ?

这篇关于动态数组传递给函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！