mekusigjinn
Idiomatic way to make ecto schema validate has_many relation AND has at least one association?
If SchemaA has_many SchemaB, what is the typical approach to validate if at least one SchemaB is associated to SchemaA?
For instance if I do
SchemaA.changeset(schema_a)
I want the resulting %Ecto.Changeset{errors: ____} to show error related to this issue if no SchemaB is associated.
Thanks in advance!
Most Liked
tfwright
Have you checked out Changeset.add_error? It should allow you to add whatever errors you like depending on the state of the changeset or underlying data if you use it in combination with get_field and/or get_change. So for example if you want to validate that on create at least one B will be associated you can do
changeset =
changeset
|> preload(:bs)
|> cast(params, [])
|> cast_assoc([:bs], with: &B.changeset/2)
changeset =
changeset
|> get_change(:bs)
|> case do
[] -> add_error(changeset, :bs, "is required") # this might need to be nil not sure
_ -> changeset
end
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