Contents

• Public Functions
• Detailed Description

Detailed Description

TheQAbstractFileEngineIterator class provides an iterator interface for custom file engines.

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

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

You can subclassQAbstractFileEngineIterator 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 ofQAbstractFileEngine::beginEntryList().

Example:

QAbstractFileEngineIterator*CustomFileEngine::beginEntryList(QDir::Filters filters,constQStringList&filterNames){returnnew 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, andfilters() to get the entry filters.

The pure virtual functionhasNext() 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. Reimplementnext() to seek to the next entry.

The pure virtual functioncurrentFileName() returns the name of the current entry without advancing the iterator. ThecurrentFilePath() 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 :publicQAbstractFileEngineIterator{public:    CustomIterator(constQStringList&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    {return index< entries.size()-1;    }QString next()    {if (!hasNext())returnQString();++index;return currentFilePath();    }QString currentFileName()    {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.

Member Function Documentation

QAbstractFileEngineIterator::QAbstractFileEngineIterator(QDir::Filters filters, constQStringList & nameFilters)

Constructs aQAbstractFileEngineIterator, using the entry filtersfilters, and wildcard name filtersnameFilters.

[virtual]QAbstractFileEngineIterator::~QAbstractFileEngineIterator()

Destroys theQAbstractFileEngineIterator.

See alsoQDirIterator.

[virtual]QFileInfo QAbstractFileEngineIterator::currentFileInfo() const

The virtual function returns aQFileInfo for the current directory entry. This function is provided for convenience. It can also be slightly faster than creating aQFileInfo object yourself, as the object returned by this function might contain cached information thatQFileInfo otherwise would have to access through the file engine.

See alsocurrentFileName().

[pure virtual]QString QAbstractFileEngineIterator::currentFileName() const

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

See alsocurrentFilePath().

QString QAbstractFileEngineIterator::currentFilePath() const

Returns the path to the current directory entry. It's the same as prependingpath() to the return value ofcurrentFileName().

See alsocurrentFileName().

QDir::Filters QAbstractFileEngineIterator::filters() const

Returns the entry filters for this iterator.

See alsoQDir::filter(),nameFilters(), andpath().

[pure virtual]bool QAbstractFileEngineIterator::hasNext() const

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).

See alsoQDirIterator::hasNext().

QStringList QAbstractFileEngineIterator::nameFilters() const

Returns the name filters for this iterator.

See alsoQDir::nameFilters(),filters(), andpath().

[pure virtual]QString QAbstractFileEngineIterator::next()

This pure virtual function advances the iterator to the next directory entry, and returns the file path to the current entry.

This function can optionally make use ofnameFilters() andfilters() to optimize its performance.

Reimplement this function in a subclass to advance the iterator.

See alsoQDirIterator::next().

QString QAbstractFileEngineIterator::path() const

Returns the path for this iterator.QDirIterator is responsible for assigning this path; it cannot change during the iterator's lifetime.

See alsonameFilters() andfilters().