Comments on: Many to many and upserts

By: josevalim

josevalim — Tue, 21 Feb 2017 10:18:00 +0000

I believe we forgot this:

many_to_many :tags, MyApp.Tag, join_through: “posts_tags”, on_replace: :delete

I.e. if you follow the instructions in your error message, it will mention about the `:on_replace` option and in this case we want to delete tags we no longer pass.

Thanks for the comment and let us know how it goes!

By: Jesper Christiansen

Jesper Christiansen — Tue, 21 Feb 2017 02:47:00 +0000

I’m a bit confused.. So for the creation of a new record, I provide a list of tags as a string “tag1, tag2” etc. But when I go to edit the post I just created, do I need to do something special for the tags? I get an error the second I load the /edit route.

def edit(conn, %{“id” => id}) do
post = Repo.get!(Post, id)
|> Repo.preload([:tags])

changeset = Post.changeset(post)
render(conn, “edit.html”, post: post, changeset: changeset)
end

That gives me the following error on load:

you are attempting to change relation :tags of App.Post, but there is missing data.
If you are attempting to update an existing entry, please make sure
you include the entry primary key (ID) alongside the data. etc etc etc

What am I doing wrong? :/

By: josevalim

josevalim — Tue, 27 Dec 2016 14:52:00 +0000

In reply to Hassan Zaki. Fixed, thank you!

By: josevalim

josevalim — Tue, 27 Dec 2016 14:51:00 +0000

In reply to evuez. If the database is not returning it, then there is nothing Ecto can do. :S

By: Hassan Zaki

Hassan Zaki — Tue, 27 Dec 2016 14:09:00 +0000

Thanks for the great post.

There’s a missing “(” in insert_and_get_all/1

Repo.all(from t in MyApp.Tag, where: t.name in ^names)

By: evuez

evuez — Tue, 27 Dec 2016 12:44:00 +0000

Being able to do an upsert is pretty cool, but with binary ids if I do an upsert on an existing row, the returned struct contains a newly generated id instead of the existing one (which kinda makes sense but is not that useful). Is there a way to get the actual id back in the same query?

Thanks for the article anyway 🙂