benonymus
Is this the correct way of creating multiple items from an array inside a multi?
Hey, i have this code:
Multi.new()
|> Multi.insert(:poll, poll_changeset(attrs))
|> Multi.run(:poll_with_hash, fn _repo, %{poll: poll_changeset} ->
Utils.generate_hash_id_for_item(poll_changeset, "poll")
end)
|> Multi.run(:poll_options, fn repo, %{poll: poll} ->
Enum.each(options, fn option ->
repo.insert(poll_option_changeset(option))
|> Utils.generate_hash_id_from_changeset("poll_option")
end)
|> case do
:ok -> {:ok, nil}
:error -> {:error, "Couldn't insert options!"}
end
end)
|> Repo.transaction()
It is working as I expect it to work, I am just wondering about the part after inserting the options, that I am checking for the result, isn’t there a way that returns what is expected {:ok, value}?
Marked As Solved
LostKobrakai
The better way is using Ecto.Multi.merge and build up a to be merged multi within the callback. This allows each db action to be it‘s own step in the multi. Keep in mind that steps can have any term as name, so names like {:insert, index} are perfectly valid.
About your solution. Use at least something different to Enum.each. It simply swallows any return values of the callback and always returns :ok.
Also Liked
LostKobrakai
I would’ve switched out
Multi.merge(multi, fn %{poll: poll} ->
Multi.new()
|> Multi.insert(poll_option, poll_option_changeset(poll, option))
|> Multi.run(poll_option_with_hash, fn _repo, %{^poll_option => poll_option_changeset} ->
Utils.generate_hash_id_for_item(poll_option_changeset, "poll_option")
end)
end)
with
multi
|> Multi.run(poll_option, fn repo, %{poll: poll} ->
repo.insert(poll_option_changeset(poll, option))
end)
|> Multi.run(poll_option_with_hash, fn _repo, %{^poll_option => poll_option_changeset} ->
Utils.generate_hash_id_for_item(poll_option_changeset, "poll_option")
end)
Nothing fancy.
LostKobrakai
Probably not, but I like to preserve Ecto.Multi.merge and ….run for the cases where I need results from prev. multi steps.
LostKobrakai
If you have the list of options before executing the multi you don’t even need Ecto.Multi.merge. Just append to multi directly.
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