tags.ex

# Migration
defmodule Bookmarks.Repo.Migrations.CreateBookmark do
  use Ecto.Migration

  def change do
    create table(:bookmarks) do
      add :href, :string, null: false, size: 2000
      add :title, :string
      add :description, :text
      add :tags, {:array, :string}
      timestamps
    end
  end
end

# models
defmodule Bookmarks.Bookmark do
  use Bookmarks.Web, :model

  schema "bookmarks" do
    field :href, :string
    field :title, :string
    field :description, :string
    belongs_to :user, User
    embeds_many :tags, Bookmarks.Tag
    timestamps
  end

  @required_fields ~w(href)
  @optional_fields ~w(title description tags)

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, @required_fields, @optional_fields)
    |> validate_length(:title, max: 255)
    |> validate_length(:description, max: 2000)
    |> validate_length(:href, min: 3)
    |> validate_length(:href, max: 2000)
  end
end

defmodule Bookmarks.Tag do
  use Bookmarks.Web, :model

  embedded_schema do
    field :name, :string
  end
end

# Failing test
  test "add one tag to a bookmark" do
    changeset = Bookmark.changeset(%Bookmark{}, %{href: "http://one.io", title: "title" })

    changeset = Ecto.Changeset.put_change(changeset, :tags, [%Tag{name: "one"}])
    bookmark = Repo.insert! changeset
    assert bookmark.tags == ["one"]
  end
  
## Repo.insert fails with the following error:
     ** (FunctionClauseError) no function clause matching in Postgrex.Extensions.Binary.encode/4
     stacktrace:
       (postgrex) lib/postgrex/extensions/binary.ex:59: Postgrex.Extensions.Binary.encode(%Postgrex.TypeInfo{array_elem: 0, base_type: 0, comp_elems: [], input: "varcharin", oid: 1043, output: "varcharout", receive: "varcharrecv", send: "varcharsend", type: "varchar"}, %{id: "5e732b94-bdef-499e-91fc-07a7ec10a611", name: "one"}, 151599, {9, 4, 1})
       (postgrex) lib/postgrex/extensions/binary.ex:288: anonymous fn/3 in Postgrex.Extensions.Binary.encode_array/4
       (elixir) lib/enum.ex:1102: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3
       (postgrex) lib/postgrex/extensions/binary.ex:284: Postgrex.Extensions.Binary.encode_array/4
       (postgrex) lib/postgrex/extensions/binary.ex:256: Postgrex.Extensions.Binary.encode_array/3
       (postgrex) lib/postgrex/protocol.ex:299: anonymous fn/2 in Postgrex.Protocol.encode_params/1
       (elixir) lib/enum.ex:1043: anonymous fn/3 in Enum.map/2
       (elixir) lib/enum.ex:1387: Enum."-reduce/3-lists^foldl/2-0-"/3
       (elixir) lib/enum.ex:1043: Enum.map/2
       (postgrex) lib/postgrex/protocol.ex:294: Postgrex.Protocol.encode_params/1
       (postgrex) lib/postgrex/protocol.ex:264: Postgrex.Protocol.send_params/2
       (postgrex) lib/postgrex/protocol.ex:136: Postgrex.Protocol.message/3
       (postgrex) lib/postgrex/connection.ex:417: Postgrex.Connection.new_data/2
       (postgrex) lib/postgrex/connection.ex:292: Postgrex.Connection.handle_info/2
       (stdlib) gen_server.erl:615: :gen_server.try_dispatch/4
       (stdlib) gen_server.erl:681: :gen_server.handle_msg/5
       (stdlib) proc_lib.erl:240: :proc_lib.init_p_do_apply/3