Thomas Weidner created FREEMARKER-43:
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Summary: Consider adding a Java 8 Style forEach method to
TemplateCollectionModel/TemplateSequenceModel
Key: FREEMARKER-43
URL: https://issues.apache.org/jira/browse/FREEMARKER-43
Project: Apache Freemarker
Issue Type: Improvement
Components: engine
Affects Versions: 2.3.25-incubating
Reporter: Thomas Weidner
Priority: Minor
I have a lot of "tuple-like" types in my model. For example:
{code:java}
class Tuple {
int a;
float b;
String c;
}
{code}
In the template, i would like to iterate through the components of tuple using
#list. To implement TemplateSequenceModel or TemplateCollectionModel, I
basically need to create a temporary List object from the tuple, which seems
unnecessary.
Java 8 added a forEach model to java.lang.Iterable, which could be easily
implemented for Tuple without temporary objects:
{code:java}
// in Tuple
void forEach(Consumer<Object> c) {
c.accept(a);
c.accept(b);
c.accept(c);
}
{code}
Unfortunately, there is no such method in
TemplateSequenceModel/TemplateCollectionModel.
I propose to add such a method to the both classes and use this method in
IteratorBlock instead of handcrafted iteration. This would allow to more
efficient iteration for custom classes, while not imposing worse performance on
"standard" collections/interfaces (these also provide forEach in java8).
As this change would require java8, this API change would not break existing
implementations of Template*Model, as forEach could be implemented as default
interface method.
I could provide a prototype patch if requested.
Maybe as a separate bug, Template{Collection,Sequence}Model should both inherit
from a new TemplateIterableModel which only provides forEach.
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