net.sf.saxon.expr
Class ContextMappingIterator
java.lang.Object
net.sf.saxon.expr.ContextMappingIterator
- SequenceIterator
public final class ContextMappingIterator
extends java.lang.Object
ContextMappingIterator merges a sequence of sequences into a single flat
sequence. It takes as inputs an iteration, and a mapping function to be
applied to each Item returned by that iteration. The mapping function itself
returns another iteration. The result is an iteration of the concatenation of all
the iterations returned by the mapping function.
This is a specialization of the MappingIterator class: it differs in that it
sets each item being processed as the context item
Item | current() - Get the current value in the sequence (the one returned by the
most recent call on next()).
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SequenceIterator | getAnother() - Get another SequenceIterator that iterates over the same items as the original,
but which is repositioned at the start of the sequence.
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int | getProperties() - Get properties of this iterator, as a bit-significant integer.
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Item | next() - Get the next item in the sequence.
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int | position() - Get the current position.
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ContextMappingIterator
public ContextMappingIterator(ContextMappingFunction action,
XPathContext context)
Construct a ContextMappingIterator that will apply a specified ContextMappingFunction to
each Item returned by the base iterator.
action
- the mapping function to be appliedcontext
- the processing context. The mapping function is applied to each item returned
by context.getCurrentIterator() in turn.
current
public Item current()
Get the current value in the sequence (the one returned by the
most recent call on next()). This will be null before the first
call of next(). This method does not change the state of the iterator.
- current in interface SequenceIterator
- the current item, the one most recently returned by a call on
next(). Returns null if next() has not been called, or if the end
of the sequence has been reached.
getAnother
public SequenceIterator getAnother()
throws XPathException
Get another SequenceIterator that iterates over the same items as the original,
but which is repositioned at the start of the sequence.
This method allows access to all the items in the sequence without disturbing the
current position of the iterator. Internally, its main use is in evaluating the last()
function.
This method does not change the state of the iterator.
- getAnother in interface SequenceIterator
- a SequenceIterator that iterates over the same items,
positioned before the first item
getProperties
public int getProperties()
Get properties of this iterator, as a bit-significant integer.
- getProperties in interface SequenceIterator
next
public Item next()
throws XPathException
Get the next item in the sequence. This method changes the state of the
iterator, in particular it affects the result of subsequent calls of
position() and current().
- next in interface SequenceIterator
- the next item, or null if there are no more items. Once a call
on next() has returned null, no further calls should be made. The preferred
action for an iterator if subsequent calls on next() are made is to return
null again, and all implementations within Saxon follow this rule.
position
public int position()
Get the current position. This will usually be zero before the first call
on next(), otherwise it will be the number of times that next() has
been called. Once next() has returned null, the preferred action is
for subsequent calls on position() to return -1, but not all existing
implementations follow this practice. (In particular, the EmptyIterator
is stateless, and always returns 0 as the value of position(), whether
or not next() has been called.)
This method does not change the state of the iterator.
- position in interface SequenceIterator
- the current position, the position of the item returned by the
most recent call of next(). This is 1 after next() has been successfully
called once, 2 after it has been called twice, and so on. If next() has
never been called, the method returns zero. If the end of the sequence
has been reached, the value returned will always be <= 0; the preferred
value is -1.