Ecto changeset - skip nil fields

Question

How do I add a field to a changeset only if the field is not nil? I don't want to update the value in the database if the value is nil. I need to check 3 fields and only update the ones that are not nil.

current code:

  put "/products" do
    errors = {}
    IO.inspect(conn.body_params)

    product = Api.Product |> Api.Repo.get(conn.query_params["id"])
    IO.inspect(product)

    if conn.body_params["image"] do
      changeset = Api.Product.changeset(product, %{image: conn.body_params["image"]})
    end

    if conn.body_params["description"] do
      changeset = Api.Product.changeset(product, %{description: conn.body_params["description"]})
    end

    if conn.body_params["price"] do
      changeset = Api.Product.changeset(product, %{price: conn.body_params["price"]})
    end
    case Api.Repo.update(changeset) do
      {:ok, product} -> 
        errors = Tuple.append(errors, "Product updated")
      {:error, changeset} -> 
        errors = Tuple.append(errors, "Product not updated")
    end

    conn
      |> put_resp_content_type("application/json")
      |> send_resp(200, Poison.encode!(%{
          successs: "success",
          errors: Tuple.to_list(errors)
      }))
  end

Dogbert Dogbert · Accepted Answer · 2017-07-09T06:17:15

You can create a new params map with only the keys which the schema accepts and whose value is not nil using for, and pass that to changeset/2:

product = Api.Product |> Api.Repo.get(conn.query_params["id"])
params = for key <- ~w(image description price), value = conn.body_params[key], into: %{}, do: {key, value}
changeset = Api.Product.changeset(product, params)
case Api.Repo.update(changeset) do
  ...
end

Ecto changeset - skip nil fields

2 Answers