net.sf.saxon.expr
Class MappingIterator

java.lang.Object
  extended bynet.sf.saxon.expr.MappingIterator
All Implemented Interfaces:
AtomizableIterator, SequenceIterator

public final class MappingIterator
extends Object
implements SequenceIterator, AtomizableIterator

MappingIterator 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 powerful class. It is used, with different mapping functions, in a great variety of ways. It underpins the way that "for" expressions and path expressions are evaluated, as well as sequence expressions. It is also used in the implementation of the document(), key(), and id() functions.


Constructor Summary
MappingIterator(SequenceIterator base, MappingFunction action, XPathContext context, Object info)
          Construct a MappingIterator that will apply a specified MappingFunction to each Item returned by the base iterator.
 
Method Summary
 Item current()
          Get the current value in the sequence (the one returned by the most recent call on next()).
 SequenceIterator getAnother()
          Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.
 Item next()
          Get the next item in the sequence.
 int position()
          Get the current position.
 void setIsAtomizing(boolean atomizing)
          Indicate that any nodes returned in the sequence will be atomized.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

MappingIterator

public MappingIterator(SequenceIterator base,
                       MappingFunction action,
                       XPathContext context,
                       Object info)
                throws XPathException
Construct a MappingIterator that will apply a specified MappingFunction to each Item returned by the base iterator.

Parameters:
base - the base iterator
action - the mapping function to be applied
context - the processing context. This should be supplied only if each item to be processed is to become the context item. In this case "base" should be the same as context.getCurrentIterator().
info - an arbitrary object to be passed as a parameter to the mapping function each time it is called
Method Detail

next

public Item next()
          throws XPathException
Description copied from interface: SequenceIterator
Get the next item in the sequence.

Specified by:
next in interface SequenceIterator
Returns:
the next item, or null if there are no more items.
Throws:
XPathException - if an error occurs retrieving the next item

current

public Item current()
Description copied from interface: SequenceIterator
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().

Specified by:
current in interface SequenceIterator
Returns:
the current item, the one most recently returned by a call on next(); or null, if next() has not been called, or if the end of the sequence has been reached.

position

public int position()
Description copied from interface: SequenceIterator
Get the current position. This will be zero before the first call on next(), otherwise it will be the number of times that next() has been called.

Specified by:
position in interface SequenceIterator
Returns:
the current position, the position of the item returned by the most recent call of next()

getAnother

public SequenceIterator getAnother()
                            throws XPathException
Description copied from interface: SequenceIterator
Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.

Specified by:
getAnother in interface SequenceIterator
Returns:
a SequenceIterator that iterates over the same items, positioned before the first item
Throws:
XPathException - if any error occurs

setIsAtomizing

public void setIsAtomizing(boolean atomizing)
Indicate that any nodes returned in the sequence will be atomized. This means that if it wishes to do so, the implementation can return the typed values of the nodes rather than the nodes themselves. The implementation is free to ignore this hint.

Specified by:
setIsAtomizing in interface AtomizableIterator
Parameters:
atomizing - true if the caller of this iterator will atomize any nodes that are returned, and is therefore willing to accept the typed value of the nodes instead of the nodes themselves.