Ecto - Update a Record - undefined function __changeset__/0 - ecto

Question

I'm getting this error when trying to update a record with a changeset:
14:36:29.972 [error] #PID<0.341.0> running Api.Router terminated
Server: 192.168.20.3:4000 (http)
Request: PUT /products/?p_id=11&s_id=11
** (exit) an exception was raised:
** (UndefinedFunctionError) function Ecto.Query.__changeset__/0 is undefined or private
(ecto) Ecto.Query.__changeset__()
(ecto) lib/ecto/changeset.ex:422: Ecto.Changeset.do_cast/4
(api) lib/api/product_shop.ex:17: Api.ProductShop.changeset/2
(api) lib/api/router.ex:168: anonymous fn/1 in Api.Router.do_match/4
(api) lib/api/router.ex:1: Api.Router.plug_builder_call/2
(api) lib/plug/debugger.ex:123: Api.Router.call/2
(plug) lib/plug/adapters/cowboy/handler.ex:15: Plug.Adapters.Cowboy.Handler.upgrade/4
(cowboy) /Users/Ben/Development/Projects/vepo/api/deps/cowboy/src/cowboy_protocol.erl:442: :cowboy_protoco
l.execute/4
code:
pid = conn.query_params["p_id"]
sid = conn.query_params["s_id"]
price = conn.query_params["price"]
query = ProductShop |> Ecto.Query.where(p_id: ^pid)
product_shop = query |> Ecto.Query.where(s_id: ^sid)
changeset2 = Api.ProductShop.changeset(product_shop, %{price: price})
case Api.Repo.update(changeset2) do
{:ok, product_shop} ->
errors = Tuple.append(errors, "Price updated")
{:error, changeset2} ->
errors = Tuple.append(errors, "Price not updated")
end
this is the ProductShop which I want to update:
14:38:56.658 [debug] QUERY OK source="product_shops" db=1.7ms
SELECT p0."id", p0."s_id", p0."p_id", p0."not_in_shop_count", p0."price" FROM "product_shops" AS p0 []
[%Api.ProductShop{__meta__: #Ecto.Schema.Metadata<:loaded, "product_shops">,
id: 11, not_in_shop_count: 0, p_id: 11, price: 5.99, s_id: 11}]
Why am I getting the error?
my ProductShop file with changeset:
defmodule Api.ProductShop do
use Ecto.Schema
import Ecto.Changeset
import Api.Repo
import Ecto.Query
#derive {Poison.Encoder, only: [:s_id, :p_id]}
schema "product_shops" do
field :s_id, :integer
field :p_id, :integer
field :not_in_shop_count, :integer
field :price, :float
end
def changeset(product_shop, params \\ %{}) do
product_shop
|> cast(params, [:s_id, :p_id])
|> validate_required([:s_id, :p_id])
|> unique_constraint(:s_id, name: :unique_product_shop)
end
def insert_product_shop(conn, product_id, shop_id, price) do
changeset = Api.ProductShop.changeset(%Api.ProductShop{p_id: product_id, s_id: shop_id, not_in_shop_count: 0, price: price})
errors = changeset.errors
valid = changeset.valid?
case insert(changeset) do
{:ok, product_shop} ->
{:ok, product_shop}
{:error, changeset} ->
{:error, :failure}
end
end
def delete_all_from_product_shops do
from(Api.ProductShop) |> delete_all
end
def get_product_shops do
Api.ProductShop |> all
end
end
in router.ex
put "/products" do
errors = {}
IO.inspect(conn.body_params)
product = Api.Product |> Api.Repo.get(conn.query_params["p_id"])
shop = Api.Shop |> Api.Repo.get(conn.query_params["s_id"])
params = for key <- ~w(image description), value = conn.body_params[key], into: %{}, do: {key, value}
changeset = Api.Product.changeset(product, params)
case Api.Repo.update(changeset) do
{:ok, product} ->
errors = Tuple.append(errors, "Product updated")
{:error, changeset} ->
errors = Tuple.append(errors, "Product not updated")
end
pid = conn.query_params["p_id"]
sid = conn.query_params["s_id"]
price = conn.query_params["price"]
query = ProductShop |> Ecto.Query.where(p_id: ^pid)
product_shop = query |> Ecto.Query.where(s_id: ^sid)
changeset2 = Api.ProductShop.changeset(product_shop, %{price: price})
case Api.Repo.update(changeset2) do
{:ok, product_shop} ->
errors = Tuple.append(errors, "Price updated")
{:error, changeset2} ->
errors = Tuple.append(errors, "Price not updated")
end
IO.inspect(errors)
conn
|> put_resp_content_type("application/json")
|> send_resp(200, Poison.encode!(%{
successs: "success",
errors: Tuple.to_list(errors)
}))
end

Answer 1

Ecto's changeset function that you write in schema, by default works for Ecto.Schema, which means that it works for modules with defined schemas in them. After using cast it deals with Ecto.Changeset struct.
Your code tries to work with Ecto.Query in changeset function, namely here:
product_shop = query |> Ecto.Query.where(s_id: ^sid)
You should use Repo.one() at the end to have valid ProductShop struct and then you can use it in ProductShop.changeset function.
Also consider rewriting how you want to retrieve this product_shop. Please use Repo.get_by:
Repo.get_by(ProductShop, s_id: s_id, p_id: p_id)