如何在C ++中检查文件在Qt中是否存在 [英] How to check whether file exists in Qt in c++

问题描述

如何检查Qt中给定路径中是​​否存在文件?

How do I check whether a file exists in a given path or not in Qt?

我当前的代码如下:

QFile Fout("/Users/Hans/Desktop/result.txt");

if(!Fout.exists()) 
{       
  eh.handleError(8);
}  
else
{
  // ......
}

但是当我运行代码时，即使我在路径中提到的文件不存在，它也不会给出 handleError 中指定的错误消息.

But when I run the code it is not giving the error message specified in handleError even though the file I mentioned in the path does not exist.

推荐答案

(位于底部的TL； DR)

我会使用 QFileInfo 类(文档)-这正是它的目的:

I would use the QFileInfo-class (docs) - this is exactly what it is made for:

QFileInfo类提供与系统无关的文件信息.

The QFileInfo class provides system-independent file information.

QFileInfo提供有关文件名称和位置(路径)的信息在文件系统中，其访问权限以及它是目录还是目录符号链接等.文件的大小和上次修改/读取时间为也提供.QFileInfo也可以用于获取有关Qt资源.

QFileInfo provides information about a file's name and position (path) in the file system, its access rights and whether it is a directory or symbolic link, etc. The file's size and last modified/read times are also available. QFileInfo can also be used to obtain information about a Qt resource.

这是检查文件是否存在的源代码:

This is the source code to check whether a file exists:

#include <QFileInfo>

(不要忘记添加相应的 #include 语句)

bool fileExists(QString path) {
    QFileInfo check_file(path);
    // check if file exists and if yes: Is it really a file and no directory?
    if (check_file.exists() && check_file.isFile()) {
        return true;
    } else {
        return false;
    }
}

还考虑:您是否只想检查路径是否存在( exists())，还是要确保这是一个文件而不是目录( isFile())?

Also consider: Do you only want to check if the path exists (exists()) or do you want to also make sure that this is a file and not a directory (isFile())?

要小心: exists()-函数的文档说:

如果文件存在，则返回true；否则，返回true.否则返回false.

Returns true if the file exists; otherwise returns false.

注意:如果文件是指向不存在文件的符号链接，则返回false.

Note: If file is a symlink that points to a non-existing file, false is returned.

这不准确.应为:

如果路径(即文件或目录)存在，则返回true；否则，返回true.否则返回false.

Returns true if the path (i.e. file or directory) exists; otherwise returns false.

---

TL; DR

(具有上述功能的较短版本，节省了几行代码)

#include <QFileInfo>

bool fileExists(QString path) {
    QFileInfo check_file(path);
    // check if path exists and if yes: Is it really a file and no directory?
    return check_file.exists() && check_file.isFile();
}

TL; Qt的DR> = 5.2

(使用Qt 5.2中引入的 exists 作为 static ；文档说static函数的速度更快，尽管我不确定这是同样也使用 isFile()方法的情况；至少是单线的)

(using exists as a static which was introduce in Qt 5.2; the docs say the static function is faster, though I'm not sure this is still the case when also using the isFile() method; at least this is a one-liner then)

#include <QFileInfo>

// check if path exists and if yes: Is it a file and no directory?
bool fileExists = QFileInfo::exists(path) && QFileInfo(path).isFile();

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