List models are like Arrays or LinkedLists in Java. A
TemplateListModel2 gives you an ordered list of elements,
which can be iterated over, using foreach or list
syntax.
To support these operations, the TemplateListModel2
interface is more complex, as we see below. The following methods allow
FM-Classic to iterate over a list:
public TemplateIteratorModel templateIterator() throws TemplateModelException;
public void releaseIterator(TemplateIteratorModel iterator);
The templateIterator() method returns an iterator,
similar to java.util.Iterator, that can be used to iterate
over a list. If there are no elements in the list, this method can safely
return null, or the isEmpty() method can return
true.
The releaseIterator() method is called once the iterator
is no longer required. This can be useful if the list model performs
pooling of iterators. Otherwise, the implementation can be left blank.
The TemplateIteratorModel looks like the following:
public boolean hasNext() throws TemplateModelException;
public TemplateModel next() throws TemplateModelException;
The hasNext() and next() methods are used
to determine when we're at the end of a list, and to return the next
element in the list respectively. These correspond to the same method
names in the java.util.Iterator interface.
The isEmpty() method determines whether there are any
elements in the iterator model. If there aren't, the iterator is
released immediately.
The TemplateWriteableIteratorModel extends
TemplateIteratorModel to provide a writeable list model.
A TemplateListModel2 can choose to return either model from its
templateIterator method.
The TemplateWriteableIteratorModel adds the following
method:
public void set(TemplateModel model) throws TemplateModelException;
The set() method overwrites the last value returned by the
iterator's next() method.
The TemplateListModel interface provides backward
compatibility for earlier versions of FreeMarker. It should not be used
for new models.
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