- Qt 5.15
- Qt Network
- C++ Classes
- QAbstractNetworkCache
- Qt 5.15.19 Reference Documentation

# QAbstractNetworkCache Class

The QAbstractNetworkCache class provides the interface for cache implementations. More...

Header: | #include <QAbstractNetworkCache>
qmake: | QT += network
Since: | Qt 4.5
Inherited By: | QNetworkDiskCache

This class was introduced in Qt 4.5.

- List of all members, including inherited members

## Public Functions

virtual | ~QAbstractNetworkCache()
virtual qint64 | cacheSize() const = 0
virtual QIODevice * | data(const QUrl &url) = 0
virtual void | insert(QIODevice *device) = 0
virtual QNetworkCacheMetaData | metaData(const QUrl &url) = 0
virtual QIODevice * | prepare(const QNetworkCacheMetaData &metaData) = 0
virtual bool | remove(const QUrl &url) = 0
virtual void | updateMetaData(const QNetworkCacheMetaData &metaData) = 0

## Public Slots

virtual void | clear() = 0

## Protected Functions

| QAbstractNetworkCache(QObject *parent = nullptr)

## Detailed Description

QAbstractNetworkCache is the base class for every standard cache that is used by QNetworkAccessManager. QAbstractNetworkCache is an abstract class and cannot be instantiated.

See also QNetworkDiskCache.

## Member Function Documentation

### `[protected]` QAbstractNetworkCache::QAbstractNetworkCache(QObject *parent = nullptr)

Constructs an abstract network cache with the given parent.

### `[pure virtual slot]` void QAbstractNetworkCache::clear()

Removes all items from the cache. Unless there was failures clearing the cache cacheSize() should return 0 after a call to clear.

In the base class this is a pure virtual function.

See also cacheSize() and remove().

### `[virtual]` QAbstractNetworkCache::~QAbstractNetworkCache()

Destroys the cache.

Any operations that have not been inserted are discarded.

See also insert().

### `[pure virtual]` qint64 QAbstractNetworkCache::cacheSize() const

Returns the current size taken up by the cache. Depending upon the cache implementation this might be disk or memory size.

In the base class this is a pure virtual function.

See also clear().

### `[pure virtual]` QIODevice *QAbstractNetworkCache::data(const QUrl &url)

Returns the data associated with url.

It is up to the application that requests the data to delete the QIODevice when done with it.

If there is no cache for url, the url is invalid, or if there is an internal cache error `nullptr` is returned.

In the base class this is a pure virtual function.

See also metaData() and prepare().

### `[pure virtual]` void QAbstractNetworkCache::insert(QIODevice *device)

Inserts the data in device and the prepared meta data into the cache. After this function is called the data and meta data should be retrievable using data() and metaData().

To cancel a prepared inserted call remove() on the metadata's url.

In the base class this is a pure virtual function.

See also prepare() and remove().

### `[pure virtual]` QNetworkCacheMetaData QAbstractNetworkCache::metaData(const QUrl &url)

Returns the meta data for the url url.

If the url is valid and the cache contains the data for url, a valid QNetworkCacheMetaData is returned.

In the base class this is a pure virtual function.

See also updateMetaData() and data().

### `[pure virtual]` QIODevice *QAbstractNetworkCache::prepare(const QNetworkCacheMetaData &metaData)

Returns the device that should be populated with the data for the cache item metaData. When all of the data has been written insert() should be called. If metaData is invalid or the url in the metadata is invalid `nullptr` is returned.

The cache owns the device and will take care of deleting it when it is inserted or removed.

To cancel a prepared inserted call remove() on the metadata's url.

In the base class this is a pure virtual function.

See also remove(), updateMetaData(), and insert().

### `[pure virtual]` bool QAbstractNetworkCache::remove(const QUrl &url)

Removes the cache entry for url, returning true if success otherwise false.

In the base class this is a pure virtual function.

See also clear() and prepare().

### `[pure virtual]` void QAbstractNetworkCache::updateMetaData(const QNetworkCacheMetaData &metaData)

Updates the cache meta date for the metaData's url to metaData

If the cache does not contains a cache item for the url then no action is taken.

In the base class this is a pure virtual function.

See also metaData() and prepare().