c++ - 生成错误E0530初始化，预期聚合对象使用 '{..}'

Question

我正在尝试在此处创建大小为``i''的数组，其中我之前已定义(底部完整代码)

double studentScores[] = new double[i];

但是我一直收到以下错误:

initialization with '{...}' expected.

我尝试了指针方法，但是似乎无法与我的其余代码一起使用。任何帮助将不胜感激，谢谢您的时间。

int main()
{
    ifstream inData;                //input file stream variable
    ofstream outData;           //output file stream variable

    inData.open("Data.txt");        //open data file
    outData.open("testStatistics.out");

    int i = 0;
    while (inData.eof() == false)   //while you have not reached the end of the file
    {
        i++;                            //i == size of the class
    }
    double studentScores[] = new double[i];     //creates an array of the size of the number of inputs

    for (int j = 0; j < i; j++)
    {
        inData >> studentScores[j]; //read in student scores
    }

    double average1 = average(i, studentScores);
    double median1 = median(i, studentScores);

    int distribution[10] = { 0 };
    for (int v = 0; v < i; v++)         //increment distribution appropriately
    {
        int h = scoresDistribution(v, studentScores);
        distribution[h] ++;
    }

    outData << "There are " << i << "scores available." << endl;
    outData << "The average is : " << average1 << endl;
    outData << "The median is : " << median1 << endl;
    outData << "The detailed grade distribution is as follows : " << endl;

    outData << fixed << left;
    outData << setfill(' ') << setw(10) << "range" << setw(10) << " # of Students" << endl;
    int z = 100;
    int y = 90;
    for (int f = 0; f < 10; f++)
    {
        outData << setfill(' ');
        outData << setw(10) << "[" << z << " - " << y << "]";
        outData << distribution[f] << endl;
        z = z - 10;
        y = y - 10;
    }

    inData.close(); //close input data file
    outData.close(); //close output data file

    cout << "Press any key to quit…" << endl;

    cin.ignore(50, '\n');
    return 0;
}

Answer 1

double studentScores[] = new double[i];

这是无效的 C++。这看起来像是残酷的 C++/ Java混合体。

您不能在此处在堆栈上创建数组，因为这样做需要在编译时知道一个固定的大小。

现代 C++的最佳方法是使用 std::vector:

std::vector<double> studentScores;
studentScores.resize(i);

如果必须使用 new，则必须使用一个指针，因为这是 new返回的内容:

double* studentScores = new double[i];

请注意，在使用完 后，您必须自己释放:

delete[] studentScores;

在这两种情况下，如果“这似乎与我的其余代码都不起作用”，则需要修复其余的代码。您可能要问一个单独的问题，或使用搜索找到可以帮助您的问题。