zatae
I have a class Company (Echo.Schema)
defmodule MyProject.Company do
use Ecto.Schema
...
@derive {Jason.Encoder, only: [:name]}
@primary_key {:id, :binary_id, autogenerate: true}
@foreign_key_type :binary_id
schema "companies" do
field(:name, :string)
field(:count, :integer, virtual: true)
has_many(:car, Car, foreign_key: :company_id, references: :id)
timestamps()
end
...
end
When I try to convert a Company to a Map, it triggers this error:
company |> Map.from_struct()
[error] GenServer #PID<0.820.0> terminating
** (RuntimeError) cannot encode metadata from the :__meta__ field for MyProject.Fleet to JSON. This metadata is used internally by Ecto and should never be exposed externally.
You can either map the schemas to remove the :__meta__ field before encoding to JSON, or explicit list the JSON fields in your schema:
defmodule MyProject.Fleet do
# ...
@derive {Jason.Encoder, only: [:name, :title, ...]}
schema ... do
...
I don’t understand the error since @derive is set in the model ? Did I forgot to do something ?
I have set Jason as Phoenix JSON parsing lib in config/config.ex :
# Use Jason for JSON parsing in Phoenix
config :phoenix, :json_library, Jason
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adamu
Map.from_struct()is not related toJason.Encoder.Json.Encoderis a protocol for converting structs to JSON, not maps.However, both are working for me in this example:
Usage:
zatae
I redacted too much code and forgot to tell that this was passed to
push_event()right after.So my guess is that
push_eventis using Jason to turn the map into JSON. And because I already turned theCompanyinto aMapbefore, Jason doesn’t clean any fields and__meta__is still there, triggering this error.Thanks for pointing out what I was not understanding correctly!