Soprano  2.8.0
Public Member Functions | Protected Member Functions
Soprano::Iterator< T > Class Template Reference

The basic Soprano iterator class. More...

#include <Soprano/Iterator>

+ Inheritance diagram for Soprano::Iterator< T >:

List of all members.

Public Member Functions

 Iterator ()
 Iterator (IteratorBackend< T > *sti)
 Iterator (const Iterator &sti)
virtual ~Iterator ()
Iteratoroperator= (const Iterator &)
void close ()
bool next ()
current () const
operator* () const
bool isValid () const
QList< T > allElements ()

Protected Member Functions

void setBackend (IteratorBackend< T > *b)
IteratorBackend< T > * backend () const

Detailed Description

template<typename T>
class Soprano::Iterator< T >

The basic Soprano iterator class.

Iterators in Soprano are very easy to use through two methods next() and current(). Instead of the latter operator*() can also be used. Both can be called subsequetially to retrieve the current element until next() has been called again.

 Soprano::Iterator<X> it;
 while( it.next() ) {
    doSomething( *it );
    doSomethingElse( it.current() );
 }

Many backends do lock the underlying Model during iteration. Thus, it is always a good idea to cache the results if they are to be used to modify the model to prevent a deadlock:

 Soprano::StatementIterator it = model->listStatements();
 QList<Statement> allStatements = it.allElements();
 Q_FOREACH( Soprano::Statement s, allStatements ) {
    modifyTheModel( model, s );
 }

Iterators have to be closed. This can either be achieved by deleting the iterator, finishing it (next() does return false), or calling close(). Before that other operations on the Model may block.

Iterators are not thread-safe. Two threads using the same iterator may result in undefined behaviour and even crashes. An iterator needs to be closed by the same thread that opened it (except if the iterator contains special code to handle such a situation.)

Warning:
Be aware that iterators in Soprano are shared objects which means that copies of one iterator object work on the same data.
Author:
Daniele Galdi danie.nosp@m.le.g.nosp@m.aldi@.nosp@m.gmai.nosp@m.l.com
Sebastian Trueg trueg.nosp@m.@kde.nosp@m..org

Definition at line 78 of file iterator.h.


Constructor & Destructor Documentation

template<typename T>
Soprano::Iterator< T >::Iterator ( )

Creates and empty, invalid iterator.

template<typename T>
Soprano::Iterator< T >::Iterator ( IteratorBackend< T > *  sti)

Create a new Iterator instance that uses sti as backend. Iterator will take ownership of the backend.

template<typename T>
Soprano::Iterator< T >::Iterator ( const Iterator< T > &  sti)
template<typename T>
virtual Soprano::Iterator< T >::~Iterator ( ) [virtual]

Member Function Documentation

template<typename T>
Iterator& Soprano::Iterator< T >::operator= ( const Iterator< T > &  )
template<typename T>
void Soprano::Iterator< T >::close ( )

Close the iterator and release any locks on the underlying Model.

template<typename T>
bool Soprano::Iterator< T >::next ( )

Advances to the next element in the iterator.

Returns:
true if another element can be read from the iterator, false if the end has been reached.
template<typename T>
T Soprano::Iterator< T >::current ( ) const

Get the element the iterator currently points to. Be aware that a valid current element is only available if next() returned true.

Returns:
the current element.
template<typename T>
T Soprano::Iterator< T >::operator* ( ) const

Retrieve the current element in the iterator.

This is equivalent to current().

Returns:
The element the iterator currently points to or an invalid one if next has never been called.
template<typename T>
bool Soprano::Iterator< T >::isValid ( ) const
Returns:
true if the Iterator is valid, false otherwise. (An invalid iterator has no backend.)
template<typename T>
QList<T> Soprano::Iterator< T >::allElements ( )

Convenience method which extracts all elements (this does not include the elements that have already been read from the iterator) from the iterator and returns them in a list.

Be aware that after calling this method the iterator will be invalid.

Returns:
A list of all elements that rest in the iterator.
template<typename T>
void Soprano::Iterator< T >::setBackend ( IteratorBackend< T > *  b) [protected]

Set the backend to read the actual data from. A previous backend will be deleted if there are no other Iterator instances using it.

template<typename T>
IteratorBackend<T>* Soprano::Iterator< T >::backend ( ) const [protected]

The documentation for this class was generated from the following file: