Question

I have a model Campain which has many Media.

I do this:

Campain.all.medias

But get this error:

 undefined method `medias' for #<Array:0x00000004bbaf40>

How can I get all medias from Campain.all?

Answer 1

The better approach is to use this code:

Campaign.includes(:media).map(&:media)

(Used English grammar, I hope you get the main idea). This will get all in two requests.

—EDIT—

If media – is has_many assosiation, indeed the return will be in form: [[...],[..]] so in that case use flaten to make it just simple array.
In the case when there needed all Mediums that are for all Camplaign use arrays group method to collect unique or just simple uniq. This approach to use Rails classes is preferable, as it is more general and configurable, for example it will apply any default scopes, that may be on Campaign.