std::out_of_range 在设置 QLineEdit 时

Question

在我的 C++ 应用程序中，我必须 select 一个带有 QFileDialog class 的文件。然后，我验证我的文件名是否正确（必须以 "VG" 开头）。

我的文件有这样的结构：VGx-xx-xxxx-xxx-xxx.pigs

之后呢，我在关联的QLineEdit里面设置了。但是每次我select一个好的文件，它就崩溃了，我不明白为什么。

这是我的不同功能：

打开 QFILE 对话框 WINDOW

/** OPEN FILE DIALOG WINDOW  **/
void VGCCC::selectPIGSFile()
{
    QString pigsFile = QFileDialog::getOpenFileName
    (
        this,
        tr("Select PIGS file"),
        "./../VGCColorConfigurator/Inputs",
        tr("Document files (*.pigs *.igs)"),
        0,
        QFileDialog::DontUseNativeDialog
    );

    pigsPath = pigsFile;
    if(verifyPIGSFileValidity(pigsPath.toStdString()))
    {
        m_filePathLine->setText("");
        m_filePathLine->setText(pigsPath);
        m_testTextEdit->insertPlainText("File selected : "+pigsPath+"\n");
    }
    else
    {
        m_filePathLine->setText("Please select a valid PIGS (Format VGx-xx-xxxx-xxx-xxx.pigs)");
        m_testTextEdit->insertPlainText("Uncorrect PIGS file.\n");
    }
}

文件名验证

/** VERIFY SELECTED PIG FILE **/
bool VGCCC::verifyPIGSFileValidity(std::string pigsPath)
{
    splitPIGSName(pigsPath);
    std::string verification = pigsNameTable[0].erase(2,2);
    std::string headerName = "VG";

    if(!verification.compare(headerName))
    {
        m_testTextEdit->insertPlainText("PIGS name is correct");
        return true;
    }
    else
        return false;
}

拆分方法

/** SPLIT PIGS NAME INTO TABLE **/
std::string* VGCCC::splitPIGSName(std::string pigsPath)
{
    std::string pigsPathToSplit = pigsPath;
    std::string delimiter = "-";
    size_t position = 0;
    int i=0;
    std::string token;

    while ((position = pigsPathToSplit.find(delimiter)) != std::string::npos)
    {
        token = pigsPathToSplit.substr(0, position);
        std::cout << token << std::endl;
        pigsNameTable[i] = token;
        i++;
        pigsPathToSplit.erase(0, position + delimiter.length());
    }
    pigsNameTable[4] = pigsPathToSplit.c_str();
    std::cout << pigsPathToSplit << std::endl;
}

Answer 1

bool VGCCC::verifyPIGSFileValidity(std::string pigsPath)
{
    splitPIGSName(pigsPath);
    std::string verification = pigsNameTable[0].erase(2,2);
    std::string headerName = "VG";

    if(!verification.compare(headerName))
    {
        m_testTextEdit->insertPlainText("PIGS name is correct");
        return true;
    }
    else
        return false;
}

不安全，因为：

1- 您不检查 pigsNameTable 是否在索引处（如果 vector？）或键（如果 map？）是否有元素 0

2- 您没有检查 pigsNameTable[0] 是否有超过 2 个元素。见 erase documentation:

pos: Position of the first character to be erased. If this is greater than the string length, it throws out_of_range.

你可以简单地做：

bool VGCCC::verifyPIGSFileValidity(std::string pigsPath)
{
    splitPIGSName(pigsPath);

    if ( /* test is pigsNameTable[0] exists depending on pigsNameTable's type */ )
    {
        return pigsNameTable[0].find( "VG" ) == 0; // return true if pigsNameTable[0] starts with "VG"
    }
    else
    {
        return false;
    }
}

如果pigsNameTable是vector，测试可以是!pigsNameTable.empty()，如果是map，pigsNameTable.find(0) != pigsNameTable.end()...

std::out_of_range 在设置 QLineEdit 时

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