SetRelation() behavior

[setanarut]

I add a component first and then make a relation assignment, but Map.SetRelation() does not seem to exhibit the expected behavior. Is this normal? // panic: relations must be fully specified

mapper := ecs.NewMap2[ChildOf, Position](&world)
mapperChildOf := ecs.NewMap[ChildOf](&world)

parent := world.NewEntity()
child := mapper.NewEntity(&ChildOf{}, &Position{})

mapperChildOf.SetRelation(child, parent)
// panic: relations must be fully specified

mapperChildOf.SetRelation(child, parent2) returns an error if parent has not been assigned before.

world := ecs.NewWorld(10)

mapper := ecs.NewMap2[ChildOf, Position](&world)
mapperChildOf := ecs.NewMap[ChildOf](&world)

parent := world.NewEntity()
parent2 := world.NewEntity()
child := mapper.NewEntity(&ChildOf{}, &Position{}, ecs.Rel(0, parent))

mapperChildOf.SetRelation(child, parent2)

[mlange-42]

Hi @setanarut!
Are you sure that the error originates in this line? Because you should already need to specify the relation target in NewEntity, and the error should appear there.

Try this:

parent := world.NewEntity()
child := mapper.NewEntity(&ChildOf{}, &Position{}, RelIdx(0, parent))

[setanarut]

I get the error in the first example I shared, I already did this in the second code and there is no error.

[setanarut]

What I mean is that SetRelation() does not do what its name says.

[mlange-42]

I think it does, and this is a misunderstanding. When adding a relation component (or creating entities with such), you must specify the target.

After that, you can use Map.SetRelation to move the entity to a different target.

Please double-chack that the error really comes from Map.SetRelation, not from mapper.NewEntity.

[setanarut]

You are right, the error was in this line. I misunderstood the method, thank you.

	_ = mapper.NewEntity(&ChildOf{}, &Position{})
	// panic: relations must be fully specified

[mlange-42]

Glad that I could help. 😃

[mlange-42]

@setanarut I would like to leave answered discussions open so others with potential similar questions have a better chance finding them.