On 2010-01-18 15.11, Stanislav Muhametsin wrote:
Sounds good. I hope the core-team approves this and it will get
implemented soon! :)
For method-constraints, I'm dabbling with a Concern that implements the
check Right Now. Reasonably easy to implement, and works well. The only
missing point is that I can't ensure that it runs before all other
concerns, but for now that's acceptable to me at least.
Here's what I got in my test. Entity method looks like this:
@Assigned(false)
void assignTo( Assignee assignee );
Annotation is:
@ConstraintDeclaration
@Retention(RetentionPolicy.RUNTIME)
@Constraints(Assigned.Constraint.class)
public @interface Assigned
{
public abstract boolean value() default true;
public class Constraint
implements org.qi4j.api.constraint.Constraint<Assigned,
Assignable.Data>
{
public boolean isValid( Assigned assigned, Assignable.Data value )
{
Assignee assignee = value.assignedTo().get();
return assigned.value() == (assignee != null);
}
}
}
--
Assignable.Data is an internal mixin that has the assignedTo() association.
The concern simply looks up annotations with @ConstraintDeclaration,
instantiates the constraint, and runs it on method invocation. Very very
simple!
But like I said, this code will pretty much never be executed. What I'm
primarily after is to let my clients find the @Assigned annotation and
run it with the constraint on an entity, so that I can automatically see
what operations are valid and update my client UI accordingly.
/Rickard
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