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

virtual	~QAbstractFileEngineIterator ()
	Destroys the QAbstractFileEngineIterator.

virtual QString	next ()=0
	This pure virtual function advances the iterator to the next directory entry, and returns the file path to the current entry.

virtual bool	hasNext () const =0
	This pure virtual function returns `true` if there is at least one more entry in the current directory (i.e., the iterator path is valid and accessible, and the iterator has not reached the end of the entry list).

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 Types
enum	EntryInfoType

Protected Member Functions
virtual QVariant	entryInfo (EntryInfoType type) const

Friends
class	QDirIterator

class	QDirIteratorPrivate

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 QDirIterator instead. This class is only for custom file engine authors.

QAbstractFileEngineIterator is a unidirectional single-use virtual iterator that plugs into QDirIterator, providing transparent proxy iteration for custom file engines.

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:

QAbstractFileEngineIterator *
CustomFileEngine::beginEntryList(QDir::Filters filters, const QStringList &filterNames)
{
    return new CustomFileEngineIterator(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 hasNext() returns true if the current directory has at least one more entry (i.e., the directory name is valid and accessible, and we have not reached the end of the entry list), and false otherwise. Reimplement next() to seek to the next entry.

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 QStringList &nameFilters, QDir::Filters filters)
        : QAbstractFileEngineIterator(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 hasNext() const override
    {
        return index < entries.size() - 1;
    }
 
    QString next() override
    {
       if (!hasNext())
           return QString();
       ++index;
       return currentFilePath();
    }
 
    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: QDirIterator

Definition at line 195 of file qabstractfileengine_p.h.

Member Enumeration Documentation

◆ EntryInfoType

enum QAbstractFileEngineIterator::EntryInfoType

protected

This enum describes the different types of information that can be requested through the QAbstractFileEngineIterator::entryInfo() function.

Definition at line 213 of file qabstractfileengine_p.h.

Constructor & Destructor Documentation

◆ QAbstractFileEngineIterator()

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

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

Definition at line 903 of file qabstractfileengine.cpp.

References QAbstractFileEngineIteratorPrivate::filters, filters(), QAbstractFileEngineIteratorPrivate::nameFilters, and nameFilters().

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◆ ~QAbstractFileEngineIterator()

QAbstractFileEngineIterator::~QAbstractFileEngineIterator ( )

virtual

Destroys the QAbstractFileEngineIterator.

See also: QDirIterator

Definition at line 916 of file qabstractfileengine.cpp.

Member Function Documentation

◆ 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.

See also: currentFileName()

Reimplemented in QFSFileEngineIterator, and AndroidAbstractFileEngineIterator.

Definition at line 1000 of file qabstractfileengine.cpp.

References currentFilePath(), QAbstractFileEngineIteratorPrivate::fileInfo, QFileInfo::filePath(), and QFileInfo::setFile().

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◆ currentFileName()

QString QAbstractFileEngineIterator::currentFileName ( ) const

pure virtual

This pure virtual function returns the name of the current directory entry, excluding the path.

See also: currentFilePath()

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

Referenced by currentFilePath().

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◆ currentFilePath()

QString QAbstractFileEngineIterator::currentFilePath ( ) const

virtual

Returns the path to the current directory entry.

It's the same as prepending path() to the return value of currentFileName().

See also: currentFileName()

Reimplemented in AndroidContentFileEngineIterator, and AndroidAbstractFileEngineIterator.

Definition at line 977 of file qabstractfileengine.cpp.

References QString::append(), currentFileName(), QString::endsWith(), QString::isEmpty(), path(), and QString::prepend().

Referenced by currentFileInfo(), CustomIterator::next(), QFSFileEngineIterator::next(), QResourceFileEngineIterator::next(), and QQmlPreviewFileEngineIterator::next().

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◆ entryInfo()

QVariant QAbstractFileEngineIterator::entryInfo ( EntryInfoType type ) const

protectedvirtual

Returns the entry info type for this iterator's current directory entry as a QVariant. If type is undefined for this entry, a null QVariant is returned.

See also: QAbstractFileEngine::beginEntryList(), QDir::beginEntryList()

Definition at line 1019 of file qabstractfileengine.cpp.

References Q_UNUSED.

◆ filters()

QDir::Filters QAbstractFileEngineIterator::filters ( ) const

Returns the entry filters for this iterator.

See also: QDir::filter(), nameFilters(), path()

Definition at line 957 of file qabstractfileengine.cpp.

References QAbstractFileEngineIteratorPrivate::filters.

Referenced by QAbstractFileEngineIterator(), and QFSFileEngineIterator::hasNext().

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◆ hasNext()

bool QAbstractFileEngineIterator::hasNext ( ) const

pure virtual

This pure virtual function returns true if there is at least one more entry in the current directory (i.e., the iterator path is valid and accessible, and the iterator has not reached the end of the entry list).