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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QDict Class Reference</h1>
<p>The QDict class is a template class that provides a
dictionary based on QString keys.
<a href="#details">More...</a>
<p><tt>#include <<a href="qdict-h.html">qdict.h</a>></tt>
<p>Inherits <a href="qptrcollection.html">QPtrCollection</a>.
<p><a href="qdict-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li class=fn><a href="#QDict"><b>QDict</b></a> ( int size = 17, bool caseSensitive = TRUE )</li>
<li class=fn><a href="#QDict-2"><b>QDict</b></a> ( const QDict<type> & dict )</li>
<li class=fn><a href="#~QDict"><b>~QDict</b></a> ()</li>
<li class=fn>QDict<type> & <a href="#operator-eq"><b>operator=</b></a> ( const QDict<type> & dict )</li>
<li class=fn>virtual uint <a href="#count"><b>count</b></a> () const</li>
<li class=fn>uint <a href="#size"><b>size</b></a> () const</li>
<li class=fn>bool <a href="#isEmpty"><b>isEmpty</b></a> () const</li>
<li class=fn>void <a href="#insert"><b>insert</b></a> ( const QString & key, const type * item )</li>
<li class=fn>void <a href="#replace"><b>replace</b></a> ( const QString & key, const type * item )</li>
<li class=fn>bool <a href="#remove"><b>remove</b></a> ( const QString & key )</li>
<li class=fn>type * <a href="#take"><b>take</b></a> ( const QString & key )</li>
<li class=fn>type * <a href="#find"><b>find</b></a> ( const QString & key ) const</li>
<li class=fn>type * <a href="#operator[]"><b>operator[]</b></a> ( const QString & key ) const</li>
<li class=fn>virtual void <a href="#clear"><b>clear</b></a> ()</li>
<li class=fn>void <a href="#resize"><b>resize</b></a> ( uint newsize )</li>
<li class=fn>void <a href="#statistics"><b>statistics</b></a> () const</li>
</ul>
<h2>Important Inherited Members</h2>
<ul>
<li class=fn>bool <a href="#autoDelete"><b>autoDelete</b></a> () const</li>
<li class=fn>void <a href="#setAutoDelete"><b>setAutoDelete</b></a> ( bool enable )</li>
</ul>
<h2>Protected Members</h2>
<ul>
<li class=fn>virtual QDataStream & <a href="#read"><b>read</b></a> ( QDataStream & s, QPtrCollection::Item & item )</li>
<li class=fn>virtual QDataStream & <a href="#write"><b>write</b></a> ( QDataStream & s, QPtrCollection::Item ) const</li>
</ul>
<hr><a name="details"></a><h2>Detailed Description</h2>
The QDict class is a template class that provides a
dictionary based on <a href="qstring.html">QString</a> keys.
<p>
<p>
<p> <a href="qmap.html">QMap</a> is an STL-compatible alternative to this class.
<p> QDict is implemented as a template class. Define a template
instance QDict<X> to create a dictionary that operates on
pointers to X (X *).
<p> A dictionary is a collection of key-value pairs. The key is a
QString used for insertion, removal and lookup. The value is a
pointer. Dictionaries provide very fast insertion and lookup.
<p> If you want to use non-Unicode, plain 8-bit <tt>char*</tt> keys, use the
<a href="qasciidict.html">QAsciiDict</a> template. A QDict has the same performance as a
QAsciiDict. If you want to have a dictionary that maps QStrings to
QStrings use QMap.
<p> The <a href="#size">size</a>() of the dictionary is very important. In order to get
good performance, you should use a suitably large <a href="primes.html#prime">prime</a> number.
Suitable means equal to or larger than the maximum expected number
of dictionary items. Size is set in the constructor but may be
changed with <a href="#resize">resize</a>().
<p> Items are inserted with <a href="#insert">insert</a>(); 0 pointers cannot be inserted.
Items are removed with <a href="#remove">remove</a>(). All the items in a dictionary can
be removed with <a href="#clear">clear</a>(). The number of items in the dictionary is
returned by <a href="#count">count</a>(). If the dictionary contains no items <a href="#isEmpty">isEmpty</a>()
returns TRUE. You can change an item's value with <a href="#replace">replace</a>(). Items
are looked up with <a href="#operator[]">operator[]</a>(), or with <a href="#find">find</a>() which return a
pointer to the value or 0 if the given key does not exist. You can
take an item out of the dictionary with <a href="#take">take</a>().
<p> Calling <a href="qptrcollection.html#setAutoDelete">setAutoDelete</a>(TRUE) for a dictionary tells it to delete
items that are removed. The default behaviour is not to delete
items when they are removed.
<p> When an item is inserted, the key is converted (hashed) to an
integer index into an internal hash array. This makes lookup very
fast.
<p> Items with equal keys are allowed. When inserting two items with
the same key, only the last inserted item will be accessible (last
in, first out) until it is removed.
<p> The <a href="qdictiterator.html">QDictIterator</a> class can traverse the dictionary, but only in
an arbitrary order. Multiple iterators may independently traverse
the same dictionary.
<p> When inserting an item into a dictionary, only the pointer is
copied, not the item itself, i.e. a <a href="shclass.html#shallow-copy">shallow copy</a> is made. It is
possible to make the dictionary copy all of the item's data (a
<a href="shclass.html#deep-copy">deep copy</a>) when an item is inserted. <a href="#insert">insert</a>() calls the virtual
function <a href="qptrcollection.html#newItem">QPtrCollection::newItem</a>() for the item to be inserted.
Inherit a dictionary and reimplement <a href="qptrcollection.html#newItem">newItem</a>() if you want deep
copies.
<p> When removing a dictionary item, the virtual function
<a href="qptrcollection.html#deleteItem">QPtrCollection::deleteItem</a>() is called. QDict's default
implementation is to delete the item if auto-deletion is enabled.
<p> Example #1:
<pre>
QDict<QLineEdit> fields; // QString keys, QLineEdit* values
fields.<a href="#insert">insert</a>( "forename", new <a href="qlineedit.html">QLineEdit</a>( this ) );
fields.<a href="#insert">insert</a>( "surname", new <a href="qlineedit.html">QLineEdit</a>( this ) );
fields["forename"]->setText( "Homer" );
fields["surname"]->setText( "Simpson" );
<a href="qdictiterator.html">QDictIterator</a><QLineEdit> it( fields ); // See QDictIterator
for( ; it.<a href="qdictiterator.html#current">current</a>(); ++it )
cout << it.<a href="qdictiterator.html#currentKey">currentKey</a>() << ": " << it.<a href="qdictiterator.html#current">current</a>()->text() << endl;
cout << endl;
if ( fields["forename"] && fields["surname"] )
cout << fields["forename"]->text() << " "
<< fields["surname"]->text() << endl; // Prints "Homer Simpson"
fields.<a href="#remove">remove</a>( "forename" ); // Does not delete the line edit
if ( ! fields["forename"] )
cout << "forename is not in the dictionary" << endl;
</pre>
In this example we use a dictionary to keep track of the line
edits we're using. We insert each line edit into the dictionary
with a unique name and then access the line edits via the
dictionary.
<p> Example #2:
<pre>
<a href="qstringlist.html">QStringList</a> styleList = QStyleFactory::styles();
styleList.<a href="qstringlist.html#sort">sort</a>();
QDict<int> letterDict( 17, FALSE );
for ( QStringList::Iterator it = styleList.<a href="qvaluelist.html#begin">begin</a>(); it != styleList.<a href="qvaluelist.html#end">end</a>(); ++it ) {
<a href="qstring.html">QString</a> styleName = *it;
<a href="qstring.html">QString</a> styleAccel = styleName;
if ( letterDict[styleAccel.<a href="qstring.html#left">left</a>(1)] ) {
for ( uint i = 0; i < styleAccel.<a href="qstring.html#length">length</a>(); i++ ) {
if ( ! letterDict[styleAccel.<a href="qstring.html#mid">mid</a>( i, 1 )] ) {
styleAccel = styleAccel.<a href="qstring.html#insert">insert</a>( i, '&' );
letterDict.<a href="#insert">insert</a>(styleAccel.<a href="qstring.html#mid">mid</a>( i, 1 ), (const int *)1);
break;
}
}
} else {
styleAccel = "&" + styleAccel;
letterDict.<a href="#insert">insert</a>(styleAccel.<a href="qstring.html#left">left</a>(1), (const int *)1);
}
(void) new <a href="qaction.html">QAction</a>( styleName, QIconSet(), styleAccel, parent );
}
</pre>
In the example we are using the dictionary to provide fast random
access to the keys, and we don't care what the values are. The
example is used to generate a menu of QStyles, each with a unique
accelerator key (or no accelerator if there are no unused letters
left).
<p> We first obtain the list of available styles, then sort them so
that the menu items will be ordered alphabetically. Next we create
a dictionary of int pointers. The keys in the dictionary are each
one character long, representing letters that have been used for
accelerators. We iterate through our list of style names. If the
first letter of the style name is in the dictionary, i.e. has been
used, we iterate over all the characters in the style name to see
if we can find a letter that hasn't been used. If we find an
unused letter we put the accelerator ampersand (&) in front of it
and add that letter to the dictionary. If we can't find an unused
letter the style will simply have no accelerator. If the first
letter of the style name is not in the dictionary we use it for
the accelerator and add it to the dictionary. Finally we create a
<a href="qaction.html">QAction</a> for each style.
<p> <p>See also <a href="qdictiterator.html">QDictIterator</a>, <a href="qasciidict.html">QAsciiDict</a>, <a href="qintdict.html">QIntDict</a>, <a href="qptrdict.html">QPtrDict</a>, <a href="collection.html">Collection Classes</a>, and <a href="tools.html">Non-GUI Classes</a>.
<hr><h2>Member Function Documentation</h2>
<h3 class=fn><a name="QDict"></a>QDict::QDict ( int size = 17, bool caseSensitive = TRUE )
</h3>
<p> Constructs a dictionary optimized for less than <em>size</em> entries.
<p> We recommend setting <em>size</em> to a suitably large <a href="primes.html#prime">prime</a> number
(e.g. a prime that's slightly larger than the expected number of
entries). This makes the hash distribution better which will lead
to faster lookup.
<p> If <em>caseSensitive</em> is TRUE (the default), keys which differ only
by case are considered different.
<h3 class=fn><a name="QDict-2"></a>QDict::QDict ( const <a href="qdict.html">QDict</a><type> & dict )
</h3>
<p> Constructs a copy of <em>dict</em>.
<p> Each item in <em>dict</em> is inserted into this dictionary. Only the
pointers are copied (shallow copy).
<h3 class=fn><a name="~QDict"></a>QDict::~QDict ()
</h3>
<p> Removes all items from the dictionary and destroys it. If
<a href="qptrcollection.html#setAutoDelete">setAutoDelete</a>() is TRUE, each value is deleted. All iterators that
access this dictionary will be reset.
<p> <p>See also <a href="qptrcollection.html#setAutoDelete">setAutoDelete</a>().
<h3 class=fn>bool <a name="autoDelete"></a>QPtrCollection::autoDelete () const
</h3>
<p> Returns the setting of the auto-delete option. The default is FALSE.
<p> <p>See also <a href="qptrcollection.html#setAutoDelete">setAutoDelete</a>().
<h3 class=fn>void <a name="clear"></a>QDict::clear ()<tt> [virtual]</tt>
</h3>
<p> Removes all items from the dictionary.
<p> The removed items are deleted if <a href="qptrcollection.html#setAutoDelete">auto-deletion</a> is enabled.
<p> All dictionary iterators that operate on the dictionary are reset.
<p> <p>See also <a href="#remove">remove</a>(), <a href="#take">take</a>(), and <a href="qptrcollection.html#setAutoDelete">setAutoDelete</a>().
<p>Reimplemented from <a href="qptrcollection.html#clear">QPtrCollection</a>.
<h3 class=fn>uint <a name="count"></a>QDict::count () const<tt> [virtual]</tt>
</h3>
<p> Returns the number of items in the dictionary.
<p> <p>See also <a href="#isEmpty">isEmpty</a>().
<p>Reimplemented from <a href="qptrcollection.html#count">QPtrCollection</a>.
<h3 class=fn>type * <a name="find"></a>QDict::find ( const <a href="qstring.html">QString</a> & key ) const
</h3>
<p> Returns the item with key <em>key</em>, or 0 if the key does not exist
in the dictionary.
<p> If there are two or more items with equal keys, then the most
recently inserted item will be found.
<p> Equivalent to the [] operator.
<p> <p>See also <a href="#operator[]">operator[]</a>().
<h3 class=fn>void <a name="insert"></a>QDict::insert ( const <a href="qstring.html">QString</a> & key, const type * item )
</h3>
<p> Inserts the key <em>key</em> with value <em>item</em> into the dictionary.
<p> Multiple items can have the same key, in which case only the last
item will be accessible using <a href="#operator[]">operator[]</a>().
<p> <em>item</em> may not be 0.
<p> <p>See also <a href="#replace">replace</a>().
<p>Example: <a href="themes-example.html#x326">themes/themes.cpp</a>.
<h3 class=fn>bool <a name="isEmpty"></a>QDict::isEmpty () const
</h3>
<p> Returns TRUE if the dictionary is empty, i.e. <a href="#count">count</a>() == 0;
otherwise returns FALSE.
<p> <p>See also <a href="#count">count</a>().
<h3 class=fn><a href="qdict.html">QDict</a><type> & <a name="operator-eq"></a>QDict::operator= ( const <a href="qdict.html">QDict</a><type> & dict )
</h3>
<p> Assigns <em>dict</em> to this dictionary and returns a reference to this
dictionary.
<p> This dictionary is first cleared, then each item in <em>dict</em> is
inserted into this dictionary. Only the pointers are copied
(shallow copy), unless <a href="qptrcollection.html#newItem">newItem</a>() has been reimplemented.
<h3 class=fn>type * <a name="operator[]"></a>QDict::operator[] ( const <a href="qstring.html">QString</a> & key ) const
</h3>
<p> Returns the item with key <em>key</em>, or 0 if the key does not
exist in the dictionary.
<p> If there are two or more items with equal keys, then the most
recently inserted item will be found.
<p> Equivalent to the <a href="#find">find</a>() function.
<p> <p>See also <a href="#find">find</a>().
<h3 class=fn><a href="qdatastream.html">QDataStream</a> & <a name="read"></a>QDict::read ( <a href="qdatastream.html">QDataStream</a> & s, <a href="qptrcollection.html#Item">QPtrCollection::Item</a> & item )<tt> [virtual protected]</tt>
</h3>
<p> Reads a dictionary item from the stream <em>s</em> and returns a
reference to the stream.
<p> The default implementation sets <em>item</em> to 0.
<p> <p>See also <a href="#write">write</a>().
<h3 class=fn>bool <a name="remove"></a>QDict::remove ( const <a href="qstring.html">QString</a> & key )
</h3>
<p> Removes the item with <em>key</em> from the dictionary. Returns TRUE if
successful, i.e. if the item is in the dictionary; otherwise
returns FALSE.
<p> If there are two or more items with equal keys, then the last item
that was inserted will be removed.
<p> The removed item is deleted if <a href="qptrcollection.html#setAutoDelete">auto-deletion</a> is enabled.
<p> All dictionary iterators that refer to the removed item will be
set to point to the next item in the dictionary's traversal order.
<p> <p>See also <a href="#take">take</a>(), <a href="#clear">clear</a>(), and <a href="qptrcollection.html#setAutoDelete">setAutoDelete</a>().
<h3 class=fn>void <a name="replace"></a>QDict::replace ( const <a href="qstring.html">QString</a> & key, const type * item )
</h3>
<p> Replaces the value of the key, <em>key</em> with <em>item</em>.
<p> If the item does not already exist, it will be inserted.
<p> <em>item</em> may not be 0.
<p> Equivalent to:
<pre>
QDict<char> dict;
...
if ( dict.<a href="#find">find</a>( key ) )
dict.<a href="#remove">remove</a>( key );
dict.<a href="#insert">insert</a>( key, item );
</pre>
<p> If there are two or more items with equal keys, then the last item
that was inserted will be replaced.
<p> <p>See also <a href="#insert">insert</a>().
<h3 class=fn>void <a name="resize"></a>QDict::resize ( uint newsize )
</h3>
<p> Changes the size of the hash table to <em>newsize</em>. The contents of
the dictionary are preserved, but all iterators on the dictionary
become invalid.
<h3 class=fn>void <a name="setAutoDelete"></a>QPtrCollection::setAutoDelete ( bool enable )
</h3>
<p> Sets the collection to auto-delete its contents if <em>enable</em> is
TRUE and to never delete them if <em>enable</em> is FALSE.
<p> If auto-deleting is turned on, all the items in a collection are
deleted when the collection itself is deleted. This is convenient
if the collection has the only pointer to the items.
<p> The default setting is FALSE, for safety. If you turn it on, be
careful about copying the collection - you might find yourself
with two collections deleting the same items.
<p> Note that the auto-delete setting may also affect other functions
in subclasses. For example, a subclass that has a <a href="#remove">remove</a>()
function will remove the item from its data structure, and if
auto-delete is enabled, will also delete the item.
<p> <p>See also <a href="qptrcollection.html#autoDelete">autoDelete</a>().
<p>Examples: <a href="grapher-nsplugin-example.html#x2769">grapher/grapher.cpp</a>, <a href="scribble-example.html#x924">scribble/scribble.cpp</a>, and <a href="bigtable-example.html#x1291">table/bigtable/main.cpp</a>.
<h3 class=fn>uint <a name="size"></a>QDict::size () const
</h3>
<p> Returns the size of the internal hash array (as specified in the
constructor).
<p> <p>See also <a href="#count">count</a>().
<h3 class=fn>void <a name="statistics"></a>QDict::statistics () const
</h3>
<p> Debugging-only function that prints out the dictionary
distribution using <a href="qapplication.html#qDebug">qDebug</a>().
<h3 class=fn>type * <a name="take"></a>QDict::take ( const <a href="qstring.html">QString</a> & key )
</h3>
<p> Takes the item with <em>key</em> out of the dictionary without deleting
it (even if <a href="qptrcollection.html#setAutoDelete">auto-deletion</a> is enabled).
<p> If there are two or more items with equal keys, then the last item
that was inserted will be taken.
<p> Returns a pointer to the item taken out, or 0 if the key does not
exist in the dictionary.
<p> All dictionary iterators that refer to the taken item will be set
to point to the next item in the dictionary traversal order.
<p> <p>See also <a href="#remove">remove</a>(), <a href="#clear">clear</a>(), and <a href="qptrcollection.html#setAutoDelete">setAutoDelete</a>().
<h3 class=fn><a href="qdatastream.html">QDataStream</a> & <a name="write"></a>QDict::write ( <a href="qdatastream.html">QDataStream</a> & s, <a href="qptrcollection.html#Item">QPtrCollection::Item</a> ) const<tt> [virtual protected]</tt>
</h3>
<p> Writes a dictionary item to the stream <em>s</em> and returns a
reference to the stream.
<p> <p>See also <a href="#read">read</a>().
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