# `BoxTurtle.Schema.Change`
[🔗](https://github.com/twajjo/box_turtle/blob/v0.1.0/lib/schema/change.ex#L1)

Generates the write functions of `BoxTurtle.Schema.Change.API` for an Ecto schema.

Attribute maps go through the schema's changeset functions, so the schema must define them:
`changeset/2` by default, for both inserts and updates.

    defmodule MyApp.Blog.Post do
      use Ecto.Schema
      import Ecto.Changeset

      schema "posts" do
        field :title, :string
        timestamps()
      end

      def changeset(post, attrs), do: post |> cast(attrs, [:title]) |> validate_required([:title])
    end

    # delete/1 by primary key looks rows up through the sibling Query module.
    defmodule MyApp.Blog.Post.Query do
      use BoxTurtle.Schema.Query, repo: MyApp.Repo
    end

    defmodule MyApp.Blog.Post.Change do
      use BoxTurtle.Schema.Change, repo: MyApp.Repo
    end

    alias MyApp.Blog.Post

    {:ok, post} = Post.Change.create(%{title: "Hello"})
    {:error, %Ecto.Changeset{}} = Post.Change.create(%{title: nil})
    {:ok, post} = Post.Change.update(post, %{title: "Hello again"})
    {:ok, _deleted} = Post.Change.delete(post.id)
    {:error, :not_found} = Post.Change.delete(post.id)

## Options

  * `:repo` - the `Ecto.Repo` to write to. Required.
  * `:schema` - the schema module. Defaults to the parent of the using module (`MyApp.Blog.Post` above).
  * `:query` - the `BoxTurtle.Schema.Query` module used to look rows up by key in `delete/1`.
    Defaults to `<schema>.Query`.
  * `:create_changeset` - name of the schema's `fun(struct, attrs)` used by `create`. Defaults to `:changeset`.
  * `:update_changeset` - name of the schema's `fun(struct, attrs)` used by `update`. Defaults to `:changeset`.
  * `:create_opts` - options passed to `c:Ecto.Repo.insert/2`, e.g. `[on_conflict: :nothing]`.

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*Consult [api-reference.md](api-reference.md) for complete listing*