The QAbstractFileEngineIterator class provides an iterator interface for custom file engines. More...

#include <qabstractfileengine_p.h>

Inheritance diagram for QAbstractFileEngineIterator:

Collaboration diagram for QAbstractFileEngineIterator:

Public Member Functions
	QAbstractFileEngineIterator (const QString &path, QDir::Filters filters, const QStringList &nameFilters)
	Constructs a QAbstractFileEngineIterator, using the entry filters filters, and wildcard name filters nameFilters.

	QAbstractFileEngineIterator (const QString &path, QDirListing::IteratorFlags filters, const QStringList &nameFilters)

virtual	~QAbstractFileEngineIterator ()
	Destroys the QAbstractFileEngineIterator.

virtual bool	advance ()=0
	This pure virtual function advances the iterator to the next directory entry; if the operation was successful this method returns `true`, otherwise it returs `false`.

QString	path () const
	Returns the path for this iterator.

QStringList	nameFilters () const
	Returns the name filters for this iterator.

QDir::Filters	filters () const
	Returns the entry filters for this iterator.

virtual QString	currentFileName () const =0
	This pure virtual function returns the name of the current directory entry, excluding the path.

virtual QFileInfo	currentFileInfo () const
	The virtual function returns a QFileInfo for the current directory entry.

virtual QString	currentFilePath () const
	Returns the path to the current directory entry.

Protected Attributes
QFileInfo	m_fileInfo

Friends
class	QDirIterator

class	QDirIteratorPrivate

class	QDirListingPrivate

Detailed Description

The QAbstractFileEngineIterator class provides an iterator interface for custom file engines.

Since: 4.3

\inmodule QtCore

If all you want is to iterate over entries in a directory, see QDirListing instead. This class is useful only for custom file engine authors.

QAbstractFileEngineIterator is a unidirectional single-use virtual iterator that plugs into QDirListing, providing transparent proxy iteration for custom file engines (for example, QResourceFileEngine).

You can subclass QAbstractFileEngineIterator to provide an iterator when writing your own file engine. To plug the iterator into your file system, you simply return an instance of this subclass from a reimplementation of QAbstractFileEngine::beginEntryList().

Example:

QAbstractFileEngine::IteratorUniquePtr
CustomFileEngine::beginEntryList(const QString &path, QDir::Filters filters,
                                 const QStringList &filterNames)
{
    return std::make_unique<CustomFileEngineIterator>(path, filters, filterNames);
}

QAbstractFileEngineIterator is associated with a path, name filters, and entry filters. The path is the directory that the iterator lists entries in. The name filters and entry filters are provided for file engines that can optimize directory listing at the iterator level (e.g., network file systems that need to minimize network traffic), but they can also be ignored by the iterator subclass; QAbstractFileEngineIterator already provides the required filtering logics in the matchesFilters() function. You can call dirName() to get the directory name, nameFilters() to get a stringlist of name filters, and filters() to get the entry filters.

The pure virtual function advance(), as its name implies, advances the iterator to the next entry in the current directory; if the operation was successful this method returns true, otherwise it returns false. You have to reimplement this function in your sub-class to work with your file engine implementation.

The pure virtual function currentFileName() returns the name of the current entry without advancing the iterator. The currentFilePath() function is provided for convenience; it returns the full path of the current entry.

Here is an example of how to implement an iterator that returns each of three fixed entries in sequence.

class CustomIterator : public QAbstractFileEngineIterator
{
public:
    CustomIterator(const QString &path, const QStringList &nameFilters, QDir::Filters filters)
        : QAbstractFileEngineIterator(path, nameFilters, filters), index(0)
    {
        // In a real iterator, these entries are fetched from the
        // file system based on the value of path().
        entries << "entry1" << "entry2" << "entry3";
    }
 
    bool advance() override
    {
        if (entries.isEmpty())
            return false;
        if (index < entries.size() - 1) {
            ++index;
            return true;
        }
        return false;
    }
 
    QString currentFileName() override
    {
        return entries.at(index);
    }
 
private:
    QStringList entries;
    int index;
};

Note: QAbstractFileEngineIterator does not deal with QDir::IteratorFlags; it simply returns entries for a single directory.

See also: QDirListing

Definition at line 210 of file qabstractfileengine_p.h.

Constructor & Destructor Documentation

◆ QAbstractFileEngineIterator() [1/2]

QAbstractFileEngineIterator::QAbstractFileEngineIterator	(	const QString &	path,
		QDir::Filters	filters,
		const QStringList &	nameFilters )

Constructs a QAbstractFileEngineIterator, using the entry filters filters, and wildcard name filters nameFilters.

Definition at line 914 of file qabstractfileengine.cpp.

◆ QAbstractFileEngineIterator() [2/2]

QAbstractFileEngineIterator::QAbstractFileEngineIterator	(	const QString &	path,
		QDirListing::IteratorFlags	filters,
		const QStringList &	nameFilters )

Definition at line 922 of file qabstractfileengine.cpp.

◆ ~QAbstractFileEngineIterator()

QAbstractFileEngineIterator::~QAbstractFileEngineIterator ( )

virtual

Destroys the QAbstractFileEngineIterator.

See also: QDirListing

Definition at line 936 of file qabstractfileengine.cpp.

Member Function Documentation

◆ advance()

virtual bool QAbstractFileEngineIterator::advance ( )

pure virtual

This pure virtual function advances the iterator to the next directory entry; if the operation was successful this method returns true, otherwise it returs false.

This function can optionally make use of nameFilters() and filters() to optimize its performance.

Reimplement this function in a subclass to advance the iterator.

Implemented in AndroidAbstractFileEngineIterator, AndroidAbstractFileEngineIterator, AndroidContentFileEngineIterator, CustomIterator, CustomIterator, QAndroidApkFileEngineIterator, QFSFileEngineIterator, QQmlPreviewFileEngineIterator, QQmlPreviewFileEngineIterator, and QResourceFileEngineIterator.

◆ currentFileInfo()

QFileInfo QAbstractFileEngineIterator::currentFileInfo ( ) const

virtual

The virtual function returns a QFileInfo for the current directory entry.

This function is provided for convenience. It can also be slightly faster than creating a QFileInfo object yourself, as the object returned by this function might contain cached information that QFileInfo otherwise would have to access through the file engine.