QDir Detailed explanation
Preface
File and directory operations are common tasks in software development, such as traversing folders, checking whether files exist, creating folders, etc. Qt provides a powerful class—QDir, specifically used to operate directories in file systems.QDirEncapsulates multiple platform-independent file system operation methods, allowing developers to easily process files and directories in cross-platform projects.
This article will introduceQDirThe purpose of this is to list commonly used constructors and member functions, and combine code examples to help developers fully grasp theQDirHow to use it.
What is QDir?
QDiris a class of Qt, specifically used to operate directories in file systems. It provides a series of methods to manage and query directories, such as setting up the current directory, enumerating files and subdirectories in the directory, creating and deleting directories, etc.QDirMaking complex file system operations simple and efficient, while ensuring cross-platform compatibility.
QDirThe operation is based on a string path and can accept absolute or relative paths. In addition, it supports filters and sorting functions, allowing for flexible filtering and arrangement of content in a directory.
QDir constructor and common member functions
Constructor
1. Default constructor
Function prototype：
QDir();
effect：
Create a representative of the current working directoryQDirObject.
Sample code：
QDir dir; qDebug() << "Current directory:" << ();
2. Specify the constructor of the path
Function prototype：
QDir(const QString &path);
effect：
Create a path that represents the specified pathQDirObject.
parameter：
path: The directory path to represent.
Sample code：
QDir dir("/home/user/documents");
qDebug() << "Directory path:" << ();Common member functions
1. exists
Function prototype：
bool exists() const; bool exists(const QString &name) const;
effect：
Checks whether the directory or specified file exists.
parameter：
(No parameters) Check whether the current directory exists.name: The name of the file or subdirectory, check whether it exists.
Return value：
If it exists, returntrue; otherwise returnfalse。
Sample code：
QDir dir("/home/user/documents");
if (()) {
qDebug() << "Directory exists.";
}
if (("")) {
qDebug() << "File exists in the directory.";
}2. mkpath
Function prototype：
bool mkpath(const QString &path) const;
effect：
Creates all parent directories of the specified path (create the directory recursively).
parameter：
path: The path to create.
Return value：
If the directory is successfully created, returntrue; otherwise returnfalse。
Sample code：
QDir dir;
if (("/home/user/new_folder/sub_folder")) {
qDebug() << "Directories created successfully.";
}3. rmpath
Function prototype：
bool rmpath(const QString &path) const;
effect：
Delete an empty directory of the specified path.
parameter：
path: The path to delete.
Return value：
If the directory is successfully deleted, returntrue; otherwise returnfalse。
Sample code：
QDir dir;
if (("/home/user/new_folder/sub_folder")) {
qDebug() << "Directory removed successfully.";
}4. setPath
Function prototype：
void setPath(const QString &path);
effect：
set upQDirThe path represented by the object.
parameter：
path: The path to set.
Sample code：
QDir dir;
("/home/user/documents");
qDebug() << "Directory path set to:" << ();5. entryList
Function prototype：
QStringList entryList(const QStringList &nameFilters = QStringList(),
Filters filters = NoFilter,
SortFlags sort = NoSort) const;effect：
Get a list of files and subdirectories in the directory that meet the criteria.
parameter：
-
nameFilters: File name filter (e.g.*.txt）。 -
filters: Filter options (e.g.QDir::Files,QDir::Dirswait). -
sort: Sort options (such asQDir::Name,QDir::Timewait).
Return value：
Returns a list of strings containing the file and subdirectory names that match the criteria.
Sample code：
QDir dir("/home/user/documents");
QStringList filters;
filters << "*.txt" << "*.docx";
QStringList files = (filters, QDir::Files);
qDebug() << "Text and doc files:" << files;6. rename
Function prototype：
bool rename(const QString &oldName, const QString &newName);
effect：
Rename a file or subdirectory.
parameter：
-
oldName: The name of the old file or directory. -
newName: The name of the new file or directory.
Return value：
If renamed successfully, returntrue; otherwise returnfalse。
Sample code：
QDir dir("/home/user/documents");
if (("old_file.txt", "new_file.txt")) {
qDebug() << "File renamed successfully.";
}7. absolutePathandabsoluteFilePath
Function prototype：
QString absolutePath() const; QString absoluteFilePath(const QString &fileName) const;
effect：
Gets the absolute path to the current directory or the absolute path to the file.
parameter：
-
fileName: The name of the file.
Return value：
Returns a string representing the absolute path.
Sample code：
QDir dir("/home/user/documents");
qDebug() << "Absolute path:" << ();
qDebug() << "Absolute file path:" << ("");Complete sample code
Here is a complete example showing how to use itQDirOperate files and directories:
#include <QDir>
#include <QDebug>
int main() {
// Create QDir object QDir dir("/home/user/documents");
// Check whether the directory exists if (!()) {
qDebug() << "Directory does not exist.";
return -1;
}
// Create a subdirectory if (("new_folder/sub_folder")) {
qDebug() << "Sub-directories created.";
}
// Get the list of files in the directory QStringList filters;
filters << "*.txt";
QStringList files = (filters, QDir::Files);
qDebug() << "Text files:" << files;
// Rename the file if (("old_file.txt", "new_file.txt")) {
qDebug() << "File renamed.";
}
// Clear the directory if (("new_folder")) {
qDebug() << "Directory removed.";
}
return 0;
}Summarize
QDirIt is a comprehensive and flexible directory operation class, which allows developers to easily complete various tasks in the file system, such as creating, deleting, traversing directories and renaming files. By supporting filtering and sorting,QDirIt also provides fine-grained control capabilities. If your project needs to process files and directories,QDirIt is an indispensable tool.
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