<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- /tmp/qt-3.0-reggie-28534/qt-x11-free-3.0.2/doc/qdict.doc:41 -->
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>QDict Class</title>
<style type="text/css"><!--
h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm; }
a:link { color: #004faf; text-decoration: none }
a:visited { color: #672967; text-decoration: none }
body { background: #ffffff; color: black; }
--></style>
</head>
<body>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr bgcolor="#E5E5E5">
<td valign=center>
<a href="index.html">
<font color="#004faf">Home</font></a>
| <a href="classes.html">
<font color="#004faf">All Classes</font></a>
| <a href="mainclasses.html">
<font color="#004faf">Main Classes</font></a>
| <a href="annotated.html">
<font color="#004faf">Annotated</font></a>
| <a href="groups.html">
<font color="#004faf">Grouped Classes</font></a>
| <a href="functions.html">
<font color="#004faf">Functions</font></a>
</td>
<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><div class=fn><a href="#QDict"><b>QDict</b></a> ( int size = 17, bool caseSensitive = TRUE )</div></li>
<li><div class=fn><a href="#QDict-2"><b>QDict</b></a> ( const QDict<type> & dict )</div></li>
<li><div class=fn><a href="#~QDict"><b>~QDict</b></a> ()</div></li>
<li><div class=fn>QDict<type> & <a href="#operator-eq"><b>operator=</b></a> ( const QDict<type> & dict )</div></li>
<li><div class=fn>virtual uint <a href="#count"><b>count</b></a> () const</div></li>
<li><div class=fn>uint <a href="#size"><b>size</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isEmpty"><b>isEmpty</b></a> () const</div></li>
<li><div class=fn>void <a href="#insert"><b>insert</b></a> ( const QString & key, const type * item )</div></li>
<li><div class=fn>void <a href="#replace"><b>replace</b></a> ( const QString & key, const type * item )</div></li>
<li><div class=fn>bool <a href="#remove"><b>remove</b></a> ( const QString & key )</div></li>
<li><div class=fn>type * <a href="#take"><b>take</b></a> ( const QString & key )</div></li>
<li><div class=fn>type * <a href="#find"><b>find</b></a> ( const QString & key ) const</div></li>
<li><div class=fn>type * <a href="#operator[]"><b>operator[]</b></a> ( const QString & key ) const</div></li>
<li><div class=fn>virtual void <a href="#clear"><b>clear</b></a> ()</div></li>
<li><div class=fn>void <a href="#resize"><b>resize</b></a> ( uint newsize )</div></li>
<li><div class=fn>void <a href="#statistics"><b>statistics</b></a> () const</div></li>
</ul>
<h2>Important Inherited Members</h2>
<ul>
<li><div class=fn>bool <a href="#autoDelete"><b>autoDelete</b></a> () const</div></li>
<li><div class=fn>void <a href="#setAutoDelete"><b>setAutoDelete</b></a> ( bool enable )</div></li>
</ul>
<h2>Protected Members</h2>
<ul>
<li><div class=fn>virtual QDataStream & <a href="#read"><b>read</b></a> ( QDataStream & s, QPtrCollection::Item & item )</div></li>
<li><div class=fn>virtual QDataStream & <a href="#write"><b>write</b></a> ( QDataStream & s, QPtrCollection::Item ) const</div></li>
</ul>
<hr><a name="details"></a><h2>Detailed Description</h2>
<p> 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
number</a>. 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>(), and 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> QDict is implemented by QGDict as a hash array with a fixed number of
entries. Each array entry points to a singly linked list of buckets,
in which the dictionary items are stored. When an item is inserted
with a key, the key is converted (hashed) to an integer index into the
hash array. The item is inserted before the first bucket in the list
of buckets.
<p> Looking up an item is normally very fast. The key is again hashed to an
array index. Then QDict scans the list of buckets and returns the item
found or null if the item was not found. You cannot insert null pointers
into a dictionary.
<p> Items with equal keys are allowed. When inserting two items with the
same key, only the last inserted item will be visible (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 it 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;
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><char> it( extra ); // 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:
<p> <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 prime 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 in
case are considered different.
<h3 class=fn><a name="QDict-2"></a>QDict::QDict ( const <a href="qdict.html">QDict</a><type> & dict )
</h3>
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>
Returns the number of items in the dictionary.
<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 null if the key does not
exist in the dictionary.
<p> If there are two or more items with equal keys, then the last item
that was inserted 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> The key does not have to be unique. If multiple items are inserted
with the same key, only the last item will be visible.
<p> Null items are not allowed.
<p> <p>See also <a href="#replace">replace</a>().
<p>Example: <a href="themes-example.html#x343">themes/themes.cpp</a>.
<h3 class=fn>bool <a name="isEmpty"></a>QDict::isEmpty () const
</h3>
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 null if the key does not
exist in the dictionary.
<p> If there are two or more items with equal keys, then the last item
that was inserted 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>
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, or FALSE if the key does not exist in the
dictionary.
<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 traversing 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> Null items are not allowed.
<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>
Changes the size of the hashtable the <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#x2621">grapher/grapher.cpp</a>, <a href="scribble-example.html#x539">scribble/scribble.cpp</a> and <a href="bigtable-example.html#x380">table/bigtable/main.cpp</a>.
<h3 class=fn>uint <a name="size"></a>QDict::size () const
</h3>
Returns the size of the internal hash array (as specified in the
constructor).
<p>See also <a href="#count">count</a>().
<h3 class=fn>void <a name="statistics"></a>QDict::statistics () const
</h3>
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 null 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>
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>().
<!-- eof -->
<hr><p>
This file is part of the <a href="index.html">Qt toolkit</a>.
Copyright © 1995-2001
<a href="http://www.trolltech.com/">Trolltech</a>. All Rights Reserved.<p><address><hr><div align=center>
<table width=100% cellspacing=0 border=0><tr>
<td>Copyright © 2001
<a href="http://www.trolltech.com">Trolltech</a><td><a href="http://www.trolltech.com/trademarks.html">Trademarks</a>
<td align=right><div align=right>Qt version 3.0.2</div>
</table></div></address></body>
</html>
distrib
>
Mandriva
>
8.2
>
i586
>
media
>
contrib
>
by-pkgid
>
112b0974ad288f6cd55bf971ee6026a9
>
files
>
1182
