How to insert data using a mix task into parent application from a library?

Questions / Help
, , ,
1

In my current directory, I have two applications with me (Please find the Github repo here):

  1. people_feeder - A library that I’m writing to insert hardcoded dummy data into projects using a mix task
  2. profile - Just a phoenix app written to make use of the library

Inside people_feeder/lib/mix/tasks/people.insert_data, this is the code that I’ve written for my mix task to run:

defmodule Mix.Tasks.People.InsertData do
  use Mix.Task

  @all_seed_params [
    %{
      name: "Bob",
      age: 19
    },

    %{
      name: "Alice",
      age: 18
    },

    %{
      name: "Nicole",
      age: 21
    }
  ]

  def run(_argv) do
    otp_app = Application.get_env(:people_feeder, :otp_app)
    repo = Application.get_env(:people_feeder, :repo)
    schema = Application.get_env(:people_feeder, :schema)

    Application.ensure_all_started(otp_app)

    insert_people(repo, schema)
  end

  def insert_people(repo, schema) do
    Enum.map(@all_seed_params, fn seed_params ->
      schema_struct = struct(schema)
      changeset = Ecto.Changeset.change(schema_struct, seed_params)

      apply(repo, :insert, [changeset, [on_conflict: :replace_all, conflict_target: :id]])
    end)

  end
end

To make sure the mix task will run with all the configs. I have configured in profile/config/config.exs with the below configurations:

# Configuration for PeopleFeeder
config :people_feeder,
  otp_app: :profile,
  repo: Profile.Repo,
  schema: Profile.People.Person

Note: The schema and repo is present in my application.

When I run the mix task by running the command mix people.insert_data. I’m getting the below error in my console:

** (UndefinedFunctionError) function Profile.People.Person.__struct__/0 is undefined (module Profile.People.Person is not available)
    Profile.People.Person.__struct__()
    (elixir 1.14.0) lib/kernel.ex:2350: Kernel.struct/3
    (people_feeder 0.1.0) lib/mix/tasks/people.insert_data.ex:33: anonymous fn/3 in Mix.Tasks.People.InsertData.insert_people/2
    (elixir 1.14.0) lib/enum.ex:1658: Enum."-map/2-lists^map/1-0-"/2
    (mix 1.14.0) lib/mix/task.ex:421: anonymous fn/3 in Mix.Task.run_task/4
    (mix 1.14.0) lib/mix/cli.ex:84: Mix.CLI.run_task/2

I’m not sure what I’m missing. I don’t understand why my dependency is not able to call a function defined in its parent application. Can anyone please help?

2

Please let me know if you need more information

3

You need to make sure that the parent application itself is also compiled and started, because you are using its repo and its structs.

4

Thank you for the reply @benwilson512. I’m not sure how to ensure my parent application is compiled and started. I am having this line in my code written for the mix task:

Application.ensure_all_started(otp_app) # The OTP app comes from the config

Can you please tell me how do I proceed?

5

Mix.Task.run("compile") will compile the application.

6

@Marcus @benwilson512

I tried to read the documentation of Mix.Task and found out that mix tasks do not automatically start the parent application. I needed to add this below line of code in my mix task to start the parent application.

@requirements ["app.start"]
3 Likes