path: root/doc/qptrdict.doc

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** QPtrDict and QPtrDictIterator class documentation
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/*****************************************************************************
  QPtrDict documentation
 *****************************************************************************/

/*!
    \class QPtrDict
    \brief The QPtrDict class is a template class that provides a dictionary based on void* keys.

    \ingroup collection
    \ingroup tools

    \important autoDelete setAutoDelete

    QPtrDict is implemented as a template class. Define a template
    instance QPtrDict\<X\> to create a dictionary that operates on
    pointers to X (X*).

    A dictionary is a collection of key-value pairs. The key is a
    void* used for insertion, removal and lookup. The value is a
    pointer. Dictionaries provide very fast insertion and lookup.

    Example:
    \code
    QPtrDict<char> fields; // void* keys, char* values

    QLineEdit *le1 = new QLineEdit( this );
    le1->setText( "Simpson" );
    QLineEdit *le2 = new QLineEdit( this );
    le2->setText( "Homer" );
    QLineEdit *le3 = new QLineEdit( this );
    le3->setText( "45" );

    fields.insert( le1, "Surname" );
    fields.insert( le2, "Forename" );
    fields.insert( le3, "Age" );

    QPtrDictIterator<char> it( fields );
    for( ; it.current(); ++it )
	cout << it.current() << endl;
    cout << endl;

    if ( fields[le1] ) // Prints "Surname: Simpson"
	cout << fields[le1] << ": " << le1->text() << endl; 
    if ( fields[le2] ) // Prints "Forename: Homer"
	cout << fields[le2] << ": " << le2->text() << endl; 

    fields.remove( le1 ); // Removes le1 from the dictionary
    cout << le1->text() << endl; // Prints "Simpson"
    \endcode
    In this example we use a dictionary to add an extra property (a
    char*) to the line edits we're using. 

    See QDict for full details, including the choice of dictionary
    size, and how deletions are handled. 

    \sa QPtrDictIterator, QDict, QAsciiDict, QIntDict,
	\link collection.html Collection Classes\endlink
*/


/*!
    \fn QPtrDict::QPtrDict( int size )

    Constructs a dictionary using an internal hash array with the size
    \a size.

    Setting \a size to a suitably large prime number (equal to or
    greater than the expected number of entries) makes the hash
    distribution better and improves lookup performance.
*/

/*!
    \fn QPtrDict::QPtrDict( const QPtrDict<type> &dict )

    Constructs a copy of \a dict.

    Each item in \a dict is inserted into this dictionary. Only the
    pointers are copied (shallow copy).
*/

/*!
    \fn QPtrDict::~QPtrDict()

    Removes all items from the dictionary and destroys it.

    All iterators that access this dictionary will be reset.

    \sa setAutoDelete()
*/

/*!
    \fn QPtrDict<type> &QPtrDict::operator=(const QPtrDict<type> &dict)

    Assigns \a dict to this dictionary and returns a reference to this
    dictionary.

    This dictionary is first cleared and then each item in \a dict is
    inserted into the dictionary. Only the pointers are copied
    (shallow copy), unless newItem() has been reimplemented.
*/

/*!
    \fn uint QPtrDict::count() const

    Returns the number of items in the dictionary.

    \sa isEmpty()
*/

/*!
    \fn uint QPtrDict::size() const

    Returns the size of the internal hash table (as specified in the
    constructor).

    \sa count()
*/

/*!
    \fn void QPtrDict::resize( uint newsize )

    Changes the size of the hash table to \a newsize. The contents of
    the dictionary are preserved, but all iterators on the dictionary
    become invalid.
*/

/*!
    \fn bool QPtrDict::isEmpty() const

    Returns TRUE if the dictionary is empty; otherwise returns FALSE.

    \sa count()
*/

/*!
    \fn void QPtrDict::insert( void *key, const type *item )

    Inserts the \a key with the \a item into the dictionary.

    Multiple items can have the same key, in which case only the last
    item will be accessible using \l operator[]().

    \a item may not be 0.

    \sa replace()
*/

/*!
    \fn void QPtrDict::replace( void *key, const type *item )

    If the dictionary has key \a key, this key's item is replaced with
    \a item. If the dictionary doesn't contain key \a key, \a item is
    inserted into the dictionary using key \a key. 

    \a item may not be 0.

    Equivalent to
    \code
	QPtrDict<ItemType> dict;
	    ...
	if ( dict.find( key ) )
	    dict.remove( key );
	dict.insert( key, item );
    \endcode

    If there are two or more items with equal keys, then the most
    recently inserted item will be replaced.

    \sa insert()
*/

/*!
    \fn bool QPtrDict::remove( void *key ) 
    
    Removes the item associated with \a key from the dictionary.
    Returns TRUE if successful, i.e. if \a key is in the dictionary;
    otherwise returns FALSE.

    If there are two or more items with equal keys, then the most
    recently inserted item will be removed.

    The removed item is deleted if \link
    QPtrCollection::setAutoDelete() auto-deletion\endlink is enabled.

    All dictionary iterators that refer to the removed item will be
    set to point to the next item in the dictionary traversal order.

    \sa take(), clear(), setAutoDelete()
*/

/*!
    \fn type *QPtrDict::take( void *key )

    Takes the item associated with \a key out of the dictionary
    without deleting it (even if \link QPtrCollection::setAutoDelete()
    auto-deletion\endlink is enabled).

    If there are two or more items with equal keys, then the most
    recently inserted item will be removed.

    Returns a pointer to the item taken out, or 0 if the key does not
    exist in the dictionary.

    All dictionary iterators that refer to the taken item will be set
    to point to the next item in the dictionary traversal order.

    \sa remove(), clear(), setAutoDelete()
*/

/*!
    \fn void QPtrDict::clear()

    Removes all items from the dictionary.

    The removed items are deleted if \link
    QPtrCollection::setAutoDelete() auto-deletion\endlink is enabled.

    All dictionary iterators that access this dictionary will be
    reset.

    \sa remove(), take(), setAutoDelete()
*/

/*!
    \fn type *QPtrDict::find( void *key ) const

    Returns the item associated with \a key, or 0 if the key does not
    exist in the dictionary.

    If there are two or more items with equal keys, then the most
    recently inserted item will be found.

    Equivalent to operator[].

    \sa operator[]()
*/

/*!
    \fn type *QPtrDict::operator[]( void *key ) const

    Returns the item associated with \a key, or 0 if the key does not
    exist in the dictionary.

    If there are two or more items with equal keys, then the most
    recently inserted item will be found.

    Equivalent to the find() function.

    \sa find()
*/

/*!
    \fn void QPtrDict::statistics() const

    Debugging-only function that prints out the dictionary
    distribution using qDebug().
*/

/*!
    \fn QDataStream& QPtrDict::read( QDataStream &s, QPtrCollection::Item &item )

    Reads a dictionary item from the stream \a s and returns a
    reference to the stream.

    The default implementation sets \a item to 0.

    \sa write()
*/

/*!
    \fn QDataStream& QPtrDict::write( QDataStream &s, QPtrCollection::Item ) const

    Writes a dictionary item to the stream \a s and returns a
    reference to the stream.

    \sa read()
*/

/*****************************************************************************
  QPtrDictIterator documentation
 *****************************************************************************/

/*!
    \class QPtrDictIterator qptrdict.h
    \brief The QPtrDictIterator class provides an iterator for QPtrDict collections.

    \ingroup collection
    \ingroup tools

    QPtrDictIterator is implemented as a template class. Define a
    template instance QPtrDictIterator\<X\> to create a dictionary
    iterator that operates on QPtrDict\<X\> (dictionary of X*).

    Example:
    \code
    QPtrDict<char> fields;

    QLineEdit *le1 = new QLineEdit( this );
    le1->setText( "Simpson" );
    QLineEdit *le2 = new QLineEdit( this );
    le2->setText( "Homer" );
    QLineEdit *le3 = new QLineEdit( this );
    le3->setText( "45" );

    fields.insert( le1, "Surname" );
    fields.insert( le2, "Forename" );
    fields.insert( le3, "Age" );

    QPtrDictIterator<char> it( fields );
    for( ; it.current(); ++it ) {
	QLineEdit *le = (QLineEdit)it.currentKey();
	cout << it.current() << ": " << le->text() << endl;
    }
    cout << endl;

    // Output (random order):
    //	Forename: Homer
    //	Age: 45
    //	Surname: Simpson
    \endcode
    In the example we insert some line edits into a dictionary,
    associating a string with each. We then iterate over the
    dictionary printing the associated strings.

    Multiple iterators may independently traverse the same dictionary.
    A QPtrDict knows about all the iterators that are operating on the
    dictionary. When an item is removed from the dictionary, QPtrDict
    updates all iterators that refer the removed item to point to the
    next item in the traversing order.

    \sa QPtrDict
*/

/*!
    \fn QPtrDictIterator::QPtrDictIterator( const QPtrDict<type> &dict )

    Constructs an iterator for \a dict. The current iterator item is
    set to point on the first item in the \a dict.
*/

/*!
    \fn QPtrDictIterator::~QPtrDictIterator()

    Destroys the iterator.
*/

/*!
    \fn uint QPtrDictIterator::count() const

    Returns the number of items in the dictionary this iterator
    operates on.

    \sa isEmpty()
*/

/*!
    \fn bool QPtrDictIterator::isEmpty() const

    Returns TRUE if the dictionary is empty; otherwise returns FALSE.

    \sa count()
*/

/*!
    \fn type *QPtrDictIterator::toFirst()

    Sets the current iterator item to point to the first item in the
    dictionary and returns a pointer to the item. If the dictionary is
    empty, it sets the current item to 0 and returns 0.
*/

/*!
    \fn QPtrDictIterator::operator type *() const

    Cast operator. Returns a pointer to the current iterator item.
    Same as current().
*/

/*!
    \fn type *QPtrDictIterator::current() const

    Returns a pointer to the current iterator item's value.
*/

/*!
    \fn void *QPtrDictIterator::currentKey() const

    Returns the current iterator item's key.
*/

/*!
    \fn type *QPtrDictIterator::operator()()

    Makes the succeeding item current and returns the original current
    item.

    If the current iterator item was the last item in the dictionary
    or if it was 0, 0 is returned.
*/

/*!
    \fn type *QPtrDictIterator::operator++()

    Prefix ++ makes the succeeding item current and returns the new
    current item.

    If the current iterator item was the last item in the dictionary
    or if it was 0, 0 is returned.
*/

/*!
    \fn type *QPtrDictIterator::operator+=( uint jump )

    Sets the current item to the item \a jump positions after the
    current item and returns a pointer to that item.

    If that item is beyond the last item or if the dictionary is
    empty, it sets the current item to 0 and returns 0.
*/