可变大小的对象数组可能未初始化答案

【问题标题】：Variable-sized object array may not be initialized可变大小的对象数组可能未初始化
【发布时间】：2016-03-08 18:16:20
【问题描述】：

所以我必须键入一个大学课程菜单，该菜单使用字符串和数组提出一系列问题。

我目前已经输入了这个。

    #include <iostream>

    #include <fstream>

    #include <vector>

    #include <string>

using namespace std;

vector<string> populateVector();
void populateArray(string *, int &);
void menu();

int main()
{
    vector<string> collegesVector = populateVector();
    int sizeOfArray = collegesVector.size();
    string statesArray [sizeOfArray] = {};
    populateArray(statesArray, sizeOfArray);

    cout << "\nWELCOME TO MY COLLEGE AND UNIVERSITY SUMMARY PROGRAM."
    cout << "\n Press 1 to enter possible colleges and universities and the program will tell you if they appear on the list."

    system("pause>nul");


do
{
    cout << "\nPress 1 to enter possible colleges and universities and the program will tell you if they appear on the list.";
    cout << "\nPress 2 to find out how many colleges and universities appear in the state of your choice.";
    cout << "\nPress 3 to find out how many colleges and universities appear on our list in total.";
    cout << "\nPress 4 to quit";

    if (choice == 1)
{
  do
  {
      cout << "Please enter the name of your college or university. ";
      cin >> userInput;

      collegesVector(resemblance);

      if(userInput != resemblance)
        cout << "\nThe institution you've entered is not on the list.\n";
      else
        cout << "\nThe institution you've entered is on our list!.\n";



  }
}

}


vector<string> populateVector()
{
    string marker;
    string entry;
    vector<string> collegesVector;
    fstream inputFile;
    inputFile.open("colleges.txt");
    if (!inputFile)
    {
        cout << "cannot read";
        return vector<string>();
    }

    getline(inputFile, marker);

    while(!inputFile.eof())
    {
        getline(inputFile, entry);

        if(entry.length() > 0)
        {
            collegesVector.push_back(entry);
        }

    }
    inputFile.close();
    return collegesVector;
}
void populateArray(string * statesArray, int & sizeOfArray)
int statesArray[] = {};
{
    fstream inputFile;
    string marker;
    string entry;
    inputFile.open("states.txt");
    if (!inputFile)
    {
        cout << "cannot read";
        return;
    }
    getline(inputFile, marker);

    for(int i = 0; i < sizeOfArray; i++)
    {

        getline(inputFile, entry);

        if(entry.length() > 0)
        {
            statesArray[i] = entry;
        }
    }
   inputFile.close();



}

它不断给我“可变大小的对象 'statesArray' 可能未初始化错误，我真的无法指出为什么它不会：\ 非常感谢。

【问题讨论】：

这是什么：void populateArray(string * statesArray, int & sizeOfArray) int statesArray[] = {}; {...？
如果可以使用std::vector，为什么还要使用可变大小的数组扩展？
由于您已经在使用向量，因此将 statesArray 设为向量。您不能创建大小在编译时未知的普通数组。
它应该给一些大学

标签： c++

【解决方案1】：

可变长度数组（VLA）在c++ 中是非标准的。所以这条线不行：

string statesArray [sizeOfArray] = {};

对于原因，here 有一个相当好的解释。至于您的示例，由于您已经在使用std::vector，您应该简单地将statesArray 替换为std::vector<std:string>。

【讨论】：