I am trying to get a has_many :through relationship working in Ecto for a many-many relationship between a User model and Group model.
The only information I was able to find online was related to nested attributes in a post by José Valim here (which is excellent, by the way).
Since the groups already exist in the system, I was hoping to do a multiple select input. I ran into a couple issues in doing that. I don't believe that it is possible to assign the groups association in the changeset directly because I was getting an error every time I attempted to do so. My next thought was to do the work manually (finding, deleting, and inserting GroupMembership records), however I wasn't sure if this was the right path to go down, and wanted to get some advice first.
Since the code sample has quite a few lines I made a gist here.
If it's preferred that I post it in this question directly, I can certainly do that.
Thanks for all the help!
Unfortunately Ecto 1.0 does not support many to many. It means you will need to receive the IDs and manually build the intermediate association for each group you are associating to the user. We hope to make this easier in future releases.
EDIT: Ecto 2.0 supports many_to_many.