Formex

Formex is an abstract layer that helps to build forms in Phoenix and Ecto. With this library you don’t write changeset, but a separate module that declares fields of form (like in Symfony). Formex will build changeset and additional Ecto queries (to get options for <select>) for itself.

Formex also comes with helper functions for templating. For now there is only a Bootstrap 3 form template, but you can easily create your own templates.

TL;DR

Installation

mix.exs

def deps do
  [{:formex, "~> 0.3.0"}]
end

def application do
  [applications: [:formex]]
end

config/config.exs

config :formex,
  repo: App.Repo,
  translate_error: &App.ErrorHelpers.translate_error/1,
  template: Formex.Template.BootstrapHorizontal, # optional, can be overridden in a .eex template
  template_options: [ # optional, also can be overridden in the template
    left_column: "col-sm-2",
    right_column: "col-sm-10"
  ]

web/web.ex

def controller do
  quote do
    use Formex.Controller
  end
end

def view do
  quote do
    import Formex.View
  end
end

Usage

We have models Article, Category and Tag:

schema "articles" do
  field :title, :string
  field :content, :string
  field :hidden, :boolean

  belongs_to :category, App.Category
  many_to_many :tags, App.Tag, join_through: "articles_tags" #...
end
schema "categories" do
  field :name, :string
end
schema "tags" do
  field :name, :string
end

Let’s create a form for Article using Formex:

# /web/form/article_type.ex
defmodule App.ArticleType do
  use Formex.Type
  alias Formex.CustomField.SelectAssoc

  def build_form(form) do
    form
    |> add(:text_input, :title, label: "Title")
    |> add(:textarea, :content, label: "Content", phoenix_opts: [
      rows: 4
    ])
    |> add(SelectAssoc, :category_id, label: "Category", phoenix_opts: [
      prompt: "Choose a category"
    ])
    |> add(SelectAssoc, :tags, label: "Tags")
    |> add(:checkbox, :hidden, label: "Is hidden?", required: false)
    |> add_button(:submit, "Submit", phoenix_opts: [
      class: "btn-primary"
    ])
  end
end

We need to slightly modify a controller:

def new(conn, _params) do
  form = create_form(App.ArticleType, %Article{})
  render(conn, "new.html", form: form)
end

def create(conn, %{"article" => article_params}) do
  App.ArticleType
  |> create_form(%Article{}, article_params)
  |> insert_form_data
  |> case do
    {:ok, _article} ->
      conn
      |> put_flash(:info, "Article created successfully.")
      |> redirect(to: article_path(conn, :index))
    {:error, form} ->
      render(conn, "new.html", form: form)
  end
end

A template:

form.html.eex

<%= formex_form_for @form, @action, fn f -> %>
  <%= if @form.changeset.action do %>Oops, something went wrong!<% end %>

  <%= formex_row f, :name %>
  <%= formex_row f, :content %>
  <%= formex_row f, :category_id %>
  <%= formex_row f, :tags %>
  <%= formex_row f, :hidden %>
  <%= formex_row f, :submit %>

  <%# or generate all fields at once: formex_rows f %>
<% end %>

Also replace changeset: @changeset with form: @form in new.html.eex

Put an asterisk to required fields:

.required .control-label:after {
  content: &#39;*&#39;;
  margin-right: 3px;
}

The final effect:

It’s very simple, isn’t it? You don’t need to create any changeset nor write a query to get options for a Category select. Furthermore, the form code is separated from the template.

Documentation

https://hexdocs.pm/formex

Basic usage

Custom fields

Templating

TODO