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https://issues.apache.org/jira/browse/GROOVY-7869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15344084#comment-15344084
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Stanislav Poslavsky commented on GROOVY-7869:
---------------------------------------------
Great! Many thanks, this workaround works! For the future: should I consider
this behaviour (interface has more preference) as a bug or as a feature (since
in Groovy 2.2.x behaviour is different)?
> Groovy category does now work with abstract iterable classes
> ------------------------------------------------------------
>
> Key: GROOVY-7869
> URL: https://issues.apache.org/jira/browse/GROOVY-7869
> Project: Groovy
> Issue Type: Bug
> Components: groovy-runtime
> Affects Versions: 2.4.0, 2.4.1, 2.4.2, 2.4.3, 2.4.4, 2.4.5, 2.4.6, 2.4.7
> Environment: OS X/Linux/Windows
> Reporter: Stanislav Poslavsky
> Priority: Blocker
>
> If one has a simple abstract iterable class and want to overload *plus*
> operator using category, Groovy will use different implementation of 'plus'
> from that defined in the category.
> Abstract iterable class:
> {code:java}
> import java.util.Iterator;
> public abstract class MyAbstractClass implements Iterable<Number> {
> public final int num;
> public MyAbstractClass(int num) { this.num = num; }
> @Override
> public String toString() { return String.valueOf(num); }
> @Override
> public Iterator<Number> iterator() {
> //just some dummy empty iterator
> return new Iterator<Number>() {
> @Override
> public boolean hasNext() { return false; }
> @Override
> public Number next() { return null; }
> };
> }
> }
> {code}
> A single implementation:
> {code:java}
> public class MyAbstractClassImpl extends MyAbstractClass {
> public MyAbstractClassImpl(int a) { super(a); }
> }
> {code}
> Category that overloads *plus* operator:
> {code:java}
> class MyCategory {
> public static MyAbstractClass plus(MyAbstractClass a, MyAbstractClass b) {
> return new MyAbstractClassImpl(a.num + b.num);
> }
> }
> {code}
> Test case:
> {code:java}
> use(MyCategory) {
> def a = new MyAbstractClassImpl(1)
> def b = new MyAbstractClassImpl(2)
> println a + b //expected 3, but received []
> assert (a+b).num == 3 // so here we see exception
> }
> {code}
> Expected to see *3*, but instead Groovy returns empty list, since it uses
> plus operator defined for iterable, but not that is defined in MyCategory.
> There is no bug in version 2.2.x.
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