By Dmytro Nasyrov, Founder, CTO at Pharos Production Inc. And Pharos Production Inc. - Web3, blockchain, fintech, defi software development services

Arc.Ecto

Arc.Ecto provides an integration with Arc and Ecto.

Installation

Add the latest stable release to your mix.exs file:

defp deps do
  [
    {:arc_ecto, "~> 0.11.1"}
  ]
end

Then run mix deps.get in your shell to fetch the dependencies.

Usage

Add Arc.Ecto.Definition

Add a second using macro use Arc.Ecto.Definition to the top of your Arc definitions.

defmodule MyApp.Avatar do
  use Arc.Definition
  use Arc.Ecto.Definition

  # ...
end

This provides a set of functions to ease integration with Arc and Ecto. In particular:

• Definition of a custom Ecto Type responsible for storing the images.
• Url generation with a cache-busting timestamp query parameter

Add a string column to your schema

Arc attachments should be stored in a string column, with a name indicative of the attachment.

create table :users do
  add :avatar, :string
end

Add your attachment to your Ecto Schema

Add a using statement use Arc.Ecto.Schema to the top of your ecto schema, and specify the type of the column in your schema as MyApp.Avatar.Type.

Attachments can subsequently be passed to Arc's storage though a Changeset cast_attachments/3 function, following the syntax of cast/3

defmodule MyApp.User do
  use MyApp.Web, :model
  use Arc.Ecto.Schema

  schema "users" do
    field :name,   :string
    field :avatar, MyApp.Avatar.Type
  end

  @doc """
  Creates a changeset based on the `data` and `params`.

  If no params are provided, an invalid changeset is returned
  with no validation performed.
  """
  def changeset(user, params \\ :invalid) do
    user
    |> cast(params, [:name])
    |> cast_attachments(params, [:avatar])
    |> validate_required([:name, :avatar])
  end
end

Save your attachments as normal through your controller

  @doc """
  Given params of:

  %{
    "id" => 1,
    "user" => %{
      "avatar" => %Plug.Upload{
                    content_type: "image/png",
                    filename: "selfie.png",
                    path: "/var/folders/q0/dg42x390000gp/T//plug-1434/multipart-765369-5"}
    }
  }

  """
  def update(conn, %{"id" => id, "user" => user_params}) do
    user = Repo.get(User, id)
    changeset = User.changeset(user, user_params)

    if changeset.valid? do
      Repo.update(changeset)

      conn
      |> put_flash(:info, "User updated successfully.")
      |> redirect(to: user_path(conn, :index))
    else
      render conn, "edit.html", user: user, changeset: changeset
    end
  end

Retrieve the serialized url

Both public and signed urls will include the timestamp for cache busting, and are retrieved the exact same way as using Arc directly.

  user = Repo.get(User, 1)

  # To receive a single rendition:
  MyApp.Avatar.url({user.avatar, user}, :thumb)
    #=> "https://bucket.s3.amazonaws.com/uploads/avatars/1/thumb.png?v=63601457477"

  # To receive all renditions:
  MyApp.Avatar.urls({user.avatar, user})
    #=> %{original: "https://.../original.png?v=1234", thumb: "https://.../thumb.png?v=1234"}

  # To receive a signed url:
  MyApp.Avatar.url({user.avatar, user}, signed: true)
  MyApp.Avatar.url({user.avatar, user}, :thumb, signed: true)

License

Copyright 2015 Sean Stavropoulos

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.