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tqt3/doc/tqdict.doc

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/****************************************************************************
**
** TQDict and TQDictIterator class documentation
**
** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
**
** This file is part of the TQt GUI Toolkit.
**
** This file may be used under the terms of the GNU General
** Public License versions 2.0 or 3.0 as published by the Free
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** Alternatively you may (at your option) use any later version
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** and the KDE Free TQt Foundation.
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** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
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**********************************************************************/
/*****************************************************************************
TQDict documentation
*****************************************************************************/
/*!
\class TQDict
\brief The TQDict class is a template class that provides a
dictionary based on TQString keys.
\ingroup collection
\ingroup tools
\mainclass
\important autoDelete setAutoDelete
TQMap is an STL-compatible alternative to this class.
TQDict is implemented as a template class. Define a template
instance TQDict\<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
TQString used for insertion, removal and lookup. The value is a
pointer. Dictionaries provide very fast insertion and lookup.
If you want to use non-Unicode, plain 8-bit \c char* keys, use the
TQAsciiDict template. A TQDict has the same performance as a
TQAsciiDict. If you want to have a dictionary that maps TQStrings to
TQStrings use TQMap.
The size() of the dictionary is very important. In order to get
good performance, you should use a suitably large prime 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 resize().
Items are inserted with insert(); 0 pointers cannot be inserted.
Items are removed with remove(). All the items in a dictionary can
be removed with clear(). The number of items in the dictionary is
returned by count(). If the dictionary contains no items isEmpty()
returns TRUE. You can change an item's value with replace(). Items
are looked up with operator[](), or with find() 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 take().
Calling setAutoDelete(TRUE) for a dictionary tells it to delete
items that are removed. The default behaviour is not to delete
items when they are removed.
When an item is inserted, the key is converted (hashed) to an
integer index into an internal hash array. This makes lookup very
fast.
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.
The TQDictIterator class can traverse the dictionary, but only in
an arbitrary order. Multiple iterators may independently traverse
the same dictionary.
When inserting an item into a dictionary, only the pointer is
copied, not the item itself, i.e. a shallow copy is made. It is
possible to make the dictionary copy all of the item's data (a
deep copy) when an item is inserted. insert() calls the virtual
function TQPtrCollection::newItem() for the item to be inserted.
Inherit a dictionary and reimplement newItem() if you want deep
copies.
When removing a dictionary item, the virtual function
TQPtrCollection::deleteItem() is called. TQDict's default
implementation is to delete the item if auto-deletion is enabled.
Example #1:
\code
TQDict<QLineEdit> fields; // TQString keys, QLineEdit* values
fields.insert( "forename", new QLineEdit( this ) );
fields.insert( "surname", new QLineEdit( this ) );
fields["forename"]->setText( "Homer" );
fields["surname"]->setText( "Simpson" );
TQDictIterator<QLineEdit> it( fields ); // See TQDictIterator
for( ; it.current(); ++it )
cout << it.currentKey() << ": " << it.current()->text() << endl;
cout << endl;
if ( fields["forename"] && fields["surname"] )
cout << fields["forename"]->text() << " "
<< fields["surname"]->text() << endl; // Prints "Homer Simpson"
fields.remove( "forename" ); // Does not delete the line edit
if ( ! fields["forename"] )
cout << "forename is not in the dictionary" << endl;
\endcode
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.
Example #2:
\code
TQStringList styleList = TQStyleFactory::styles();
styleList.sort();
TQDict<int> letterDict( 17, FALSE );
for ( TQStringList::Iterator it = styleList.begin(); it != styleList.end(); ++it ) {
TQString styleName = *it;
TQString styleAccel = styleName;
if ( letterDict[styleAccel.left(1)] ) {
for ( uint i = 0; i < styleAccel.length(); i++ ) {
if ( ! letterDict[styleAccel.mid( i, 1 )] ) {
styleAccel = styleAccel.insert( i, '&' );
letterDict.insert(styleAccel.mid( i, 1 ), (const int *)1);
break;
}
}
} else {
styleAccel = "&" + styleAccel;
letterDict.insert(styleAccel.left(1), (const int *)1);
}
(void) new TQAction( styleName, TQIconSet(), styleAccel, parent );
}
\endcode
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 TQStyles, each with a unique
accelerator key (or no accelerator if there are no unused letters
left).
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
TQAction for each style.
\sa TQDictIterator, TQAsciiDict, TQIntDict, TQPtrDict
*/
/*!
\fn TQDict::TQDict( int size, bool caseSensitive )
Constructs a dictionary optimized for less than \a size entries.
We recommend setting \a size 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.
If \a caseSensitive is TRUE (the default), keys which differ only
by case are considered different.
*/
/*!
\fn TQDict::TQDict( const TQDict<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 TQDict::~TQDict()
Removes all items from the dictionary and destroys it. If
setAutoDelete() is TRUE, each value is deleted. All iterators that
access this dictionary will be reset.
\sa setAutoDelete()
*/
/*!
\fn TQDict<type> &TQDict::operator=(const TQDict<type> &dict)
Assigns \a dict to this dictionary and returns a reference to this
dictionary.
This dictionary is first cleared, then each item in \a dict is
inserted into this dictionary. Only the pointers are copied
(shallow copy), unless newItem() has been reimplemented.
*/
/*!
\fn uint TQDict::count() const
Returns the number of items in the dictionary.
\sa isEmpty()
*/
/*!
\fn uint TQDict::size() const
Returns the size of the internal hash array (as specified in the
constructor).
\sa count()
*/
/*!
\fn void TQDict::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 TQDict::isEmpty() const
Returns TRUE if the dictionary is empty, i.e. count() == 0;
otherwise returns FALSE.
\sa count()
*/
/*!
\fn void TQDict::insert( const TQString &key, const type *item )
Inserts the key \a key with value \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 TQDict::replace( const TQString &key, const type *item )
Replaces the value of the key, \a key with \a item.
If the item does not already exist, it will be inserted.
\a item may not be 0.
Equivalent to:
\code
TQDict<char> 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 last item
that was inserted will be replaced.
\sa insert()
*/
/*!
\fn bool TQDict::remove( const TQString &key )
Removes the item with \a key from the dictionary. Returns TRUE if
successful, i.e. if the item is in the dictionary; otherwise
returns FALSE.
If there are two or more items with equal keys, then the last item
that was inserted will be removed.
The removed item is deleted if \link
TQPtrCollection::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's traversal order.
\sa take(), clear(), setAutoDelete()
*/
/*!
\fn type *TQDict::take( const TQString &key )
Takes the item with \a key out of the dictionary without deleting
it (even if \link TQPtrCollection::setAutoDelete()
auto-deletion\endlink is enabled).
If there are two or more items with equal keys, then the last item
that was inserted will be taken.
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 TQDict::clear()
Removes all items from the dictionary.
The removed items are deleted if \link
TQPtrCollection::setAutoDelete() auto-deletion\endlink is enabled.
All dictionary iterators that operate on the dictionary are reset.
\sa remove(), take(), setAutoDelete()
*/
/*!
\fn type *TQDict::find( const TQString &key ) const
Returns the item with key \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 [] operator.
\sa operator[]()
*/
/*!
\fn type *TQDict::operator[]( const TQString &key ) const
Returns the item with key \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 TQDict::statistics() const
Debugging-only function that prints out the dictionary
distribution using tqDebug().
*/
/*!
\fn QDataStream& TQDict::read( QDataStream &s, TQPtrCollection::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& TQDict::write( QDataStream &s, TQPtrCollection::Item ) const
Writes a dictionary item to the stream \a s and returns a
reference to the stream.
\sa read()
*/
/*****************************************************************************
TQDictIterator documentation
*****************************************************************************/
/*!
\class TQDictIterator tqdict.h
\brief The TQDictIterator class provides an iterator for TQDict collections.
\ingroup collection
\ingroup tools
TQDictIterator is implemented as a template class. Define a
template instance TQDictIterator\<X\> to create a dictionary
iterator that operates on TQDict\<X\> (dictionary of X*).
The traversal order is arbitrary; when we speak of the "first",
"last" and "next" item we are talking in terms of this arbitrary
order.
Multiple iterators may independently traverse the same dictionary.
A TQDict knows about all the iterators that are operating on the
dictionary. When an item is removed from the dictionary, TQDict
updates all iterators that are referring to the removed item to
point to the next item in the (arbitrary) traversal order.
Example:
\code
TQDict<QLineEdit> fields;
fields.insert( "forename", new QLineEdit( this ) );
fields.insert( "surname", new QLineEdit( this ) );
fields.insert( "age", new QLineEdit( this ) );
fields["forename"]->setText( "Homer" );
fields["surname"]->setText( "Simpson" );
fields["age"]->setText( "45" );
TQDictIterator<QLineEdit> it( fields );
for( ; it.current(); ++it )
cout << it.currentKey() << ": " << it.current()->text() << endl;
cout << endl;
// Output (random order):
// age: 45
// surname: Simpson
// forename: Homer
\endcode
In the example we insert some pointers to line edits into a
dictionary, then iterate over the dictionary printing the strings
associated with the line edits.
\sa TQDict
*/
/*!
\fn TQDictIterator::TQDictIterator( const TQDict<type> &dict )
Constructs an iterator for \a dict. The current iterator item is
set to point to the first item in the dictionary, \a dict. First
in this context means first in the arbitrary traversal order.
*/
/*!
\fn TQDictIterator::~TQDictIterator()
Destroys the iterator.
*/
/*!
\fn uint TQDictIterator::count() const
Returns the number of items in the dictionary over which the
iterator is operating.
\sa isEmpty()
*/
/*!
\fn bool TQDictIterator::isEmpty() const
Returns TRUE if the dictionary is empty, i.e. count() == 0;
otherwise returns FALSE.
\sa count()
*/
/*!
\fn type *TQDictIterator::toFirst()
Resets the iterator, making the first item the first current item.
First in this context means first in the arbitrary traversal
order. Returns a pointer to this item.
If the dictionary is empty it sets the current item to 0 and
returns 0.
*/
/*!
\fn type *TQDictIterator::operator*()
\internal
*/
/*!
\fn TQDictIterator::operator type*() const
Cast operator. Returns a pointer to the current iterator item.
Same as current().
*/
/*!
\fn type *TQDictIterator::current() const
Returns a pointer to the current iterator item's value.
*/
/*!
\fn TQString TQDictIterator::currentKey() const
Returns the current iterator item's key.
*/
/*!
\fn type *TQDictIterator::operator()()
Makes the next 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 *TQDictIterator::operator++()
Prefix ++ makes the next 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 *TQDictIterator::operator+=( uint jump )
\internal
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.
*/