how to remove null associations when eager loading ?

[gmolveau]

Hello there, I've got this kind of schema :

Author [n] <-> [1] Post [n] <-> [1] Comment

And I would like to know how to remove null associations when using :

tx.Eager("Posts.Comments").Find(author, id)

Thank's for your help

[u007]

maybe a where clause somewhere?

[gmolveau]

Thank's for your answer. Well, if for example author_id is null, I don't want an Author object filled with nulled fields inside the Post object but rather a null Author object or nothing at all.

[u007]

right now its not a pointer attribute, unless this can be a pointer and it detects it and assign it to null.
for the moment, you may always check for AuthorID for 0 or uuid.Nil
@markbates @stanislas-m any recommendation on this?

[markbates]

Looping @larrymjordan into the conversation as he might be best placed to add color to this discussion.

[larrymjordan]

Hi @gmolveau, I got your point, this issue seems to be related to #106 and #123. I actually did a PR a couple of week ago to solve exactly that #124. As soon as it get merged I guess would solve your problem. In a meantime I can give you a strategy to solve your problem by splitting the process into two steps.

1 - Eager load all author posts like this:
tx.Eager("Posts").Find(author, id)

2- Load all comments for your posts:
tx.Load(&author.Posts, "Comments")

Let me know if that works for you.

[gmolveau]

Hey everyone thank you all for your answers ! No problem I can wait until the PR is merged.
I tried your method but I get this error :

reflect: call of reflect.Value.Elem on slice Value
github.com/gobuffalo/buffalo.(*App).PanicHandler.func1.1
	/Users/gmolveau/go/src/github.com/gobuffalo/buffalo/errors.go:61
runtime.call32
	/usr/local/Cellar/go/1.10.3/libexec/src/runtime/asm_amd64.s:573
runtime.gopanic
	/usr/local/Cellar/go/1.10.3/libexec/src/runtime/panic.go:502
reflect.Value.Elem
	/usr/local/Cellar/go/1.10.3/libexec/src/reflect/value.go:775
github.com/gobuffalo/pop.(*Query).eagerAssociations
	/Users/gmolveau/go/src/github.com/gobuffalo/pop/finders.go:185
github.com/gobuffalo/pop.(*Connection).Load
	/Users/gmolveau/go/src/github.com/gobuffalo/pop/finders.go:175

I'll just stick with what I am doing at the moment and I'll be fine untile those PR are merged.

[larrymjordan]

@gmolveau that's ok, for the error you mentioned above, it seems like you are not using "&" to reference author.Posts in the Load method?

[u007]

@larrymjordan have we added this query to documentation?

[gmolveau]

@larrymjordan you were right I forgot to use the reference, I thought that as I was using the reference of the parent I did not need to specify that I wanted the reference of the child. Thank's for your help !

[larrymjordan]

@u007 you mean https://gobuffalo.io/en/docs/db/relations#existing-model ? Not sure why it is not added to pop documentation.