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46 // This file is not part of the Qt API. It exists purely as an
47 // implementation detail. This header file may change from version to
48 // version without notice, or even be removed.
52 #ifndef Patternist_ItemMappingIterator_H
53 #define Patternist_ItemMappingIterator_H
55 #include <private/qabstractxmlforwarditerator_p.h>
56 #include <private/qdynamiccontext_p.h>
65 * @short Proxies another QAbstractXmlForwardIterator, and for each item, returns the
66 * Item returned from a mapping function.
68 * ItemMappingIterator is practical when the items in an QAbstractXmlForwardIterator needs to
69 * be translated to another sequence, while still doing it in a pipe-lined
72 * This is achieved by that ItemMappingIterator's constructor takes
73 * an instance of a class, that must have the following member:
76 * TResult::Ptr mapToItem(const TSource &item,
77 * const Context &context) const
80 * For each item in the QAbstractXmlForwardIterator ItemMappingIterator proxies, this function is
81 * called and its return value becomes the return value of the ItemMappingIterator. If the
82 * mapping function returns null, ItemMappingIterator maps the next item in the source sequence
83 * such that a contiguous sequence of items is returned.
85 * Declaring the mapToItem() function as inline, can be a good way to improve performance.
87 * @see SequenceMappingIterator
88 * @author Frans Englich <frans.englich@nokia.com>
89 * @ingroup Patternist_iterators
91 template<typename TResult, typename TSource, typename TMapper, typename Context = DynamicContext::Ptr>
92 class ItemMappingIterator : public QAbstractXmlForwardIterator<TResult>
96 * Constructs an ItemMappingIterator.
98 * @param mapper the object that has the mapToItem() sequence.
99 * @param iterator the QAbstractXmlForwardIterator whose items should be mapped.
100 * @param context the context that will be passed to the map function.
103 ItemMappingIterator(const TMapper &mapper,
104 const typename QAbstractXmlForwardIterator<TSource>::Ptr &iterator,
105 const Context &context) : m_mapper(mapper)
115 * @returns the next item in the sequence, or
116 * @c null if the end have been reached.
118 virtual TResult next()
120 const TSource sourceItem(m_it->next());
122 if(qIsForwardIteratorEnd(sourceItem))
124 m_current = TResult();
130 m_current = m_mapper->mapToItem(sourceItem, m_context);
131 if(qIsForwardIteratorEnd(m_current))
132 return next(); /* The mapper returned null, so continue with the next in the source. */
141 virtual TResult current() const
146 virtual xsInteger position() const
151 virtual typename QAbstractXmlForwardIterator<TResult>::Ptr copy() const
153 return typename QAbstractXmlForwardIterator<TResult>::Ptr
154 (new ItemMappingIterator<TResult, TSource, TMapper, Context>(m_mapper, m_it->copy(), m_context));
158 const TMapper m_mapper;
159 const typename QAbstractXmlForwardIterator<TSource>::Ptr m_it;
160 const Context m_context;
162 xsInteger m_position;
166 * @short An object generator for ItemMappingIterator.
168 * makeItemMappingIterator() is a convenience function for avoiding specifying
169 * the full template instantiation for ItemMappingIterator. Conceptually, it
170 * is identical to Qt's qMakePair().
172 * @relates ItemMappingIterator
174 template<typename TResult, typename TSource, typename TMapper, typename Context>
176 typename QAbstractXmlForwardIterator<TResult>::Ptr
177 makeItemMappingIterator(const TMapper &mapper,
178 const QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<TSource> > &source,
179 const Context &context)
181 return typename QAbstractXmlForwardIterator<TResult>::Ptr
182 (new ItemMappingIterator<TResult, TSource, TMapper, Context>(mapper, source, context));