BaseModel

BaseModel

ActiveRecord for Ecto.

{:base_model, "~> 0.2"},

BaseModel provides a straightforward __using__ macro to include common CRUD functions in your models:

• create(params)
• all()
• count(where_clause \\ :anything)
• find(id)
• first(where_clause)
• first_or_create(where_clause)
• where(where_clause)
• update(model, params)
• update_where(where_clause, params)
• delete(id_or_struct)
• delete_where(where_clause)
• delete_all

All of these are overridable, and where appropriate, support options including :limit, :preload, and :order_by. Custom create and update validation is possible by overriding create_changeset/1 or update_changeset/1 in the model.

Example

A model taken from the example app:

defmodule ExampleApp.Models.User do
  use BaseModel, repo: ExampleApp.Repo
  alias ExampleApp.Models.Problem

  schema "users" do
    field :name, :string
    field :age, :integer
    has_many :problems, Problem
    timestamps()
  end
end

Because ExampleApp.Repo has been specified in the use directive, BaseModel methods can omit it:

iex> alias ExampleApp.Models.User
...> {:ok, chris} = User.create(name: "chris")
{:ok, %User{name: "chris", age: nil}}
...> User.update(chris, age: -1)
{:ok, %User{name: "chris", age: -1}}
...> User.count
1
...> User.where(name: "chris")
[%User{name: "chris", age: -1}]

Getting Started

1. Setup your repo as you normally would, and create your models as usual.
2. To each model, add use BaseModel, repo: YourApp.Repo
3. Profit!

Associations

:belongs_to associations can be specified during create, and can be used in any query or params list, e.g.:

iex> {:ok, chris} = User.create(name: "chris")

# BaseModel will do the field mapping for you if you pass a struct to the association
...> Problem.create(user: chris, description: "...so I used regular expressions.")
# Or you could do it yourself:
...> Problem.create(user_id: chris.id, description: "now I have 100 problems.")

# In query-mode: (also works for `where`, `count`, `update_where`)
...> Problem.delete_where(user: chris)
{:ok, 2}

Opts

BaseModel methods support an optional opts parameter, which accepts 3 values:

• :preload
• :limit
• :order_by

Each of these operates as a direct pass-thru to Ecto, so see their documentation on available use. Note that these opts are sensibly applied, e.g. passing :limit to count is ignored, etc.

iex> User.find(1, preload: :problems)
%User{name: "chris", problems: []}

Overriding *_changeset methods

From the Problem model in ExampleApp

# in models/problem.ex:
schema "problems" do
  field :description, :string
  field :severity, :integer
  belongs_to :user, User
  timestamps()
end

@severities 1..5

@impl BaseModel
def create_changeset(params) do
  %__MODULE__{}
  |> cast(params, [:description, :severity, :user_id])
  |> validate_inclusion(:severity, @severities)
end

@impl BaseModel
def update_changeset(model, params) do
  model
  |> cast(params, [:description, :severity, :user_id])
  |> validate_inclusion(:severity, @severities)
end

The BaseModel method create will first extract association fields from your params, then pass them to create_changeset/1. By overriding it as we have here, custom validations can be applied, e.g. here, we’ve restricted severity to be in 1..5.

Likewise, update will call update_changeset, and use the resulting changeset in it’s call to Repo.update.

Closing comments

I wrote the first version of BaseModel back when Elixir 0.13 was the new hotness and I was missing my old friend, ActiveRecord. I’ve found this query interface suitable for many use-cases, but as soon as I have a need for a more complicated query, I simply add it as a new method on the model. This way, all of my Ecto code lives in the models, and in the models only. The sanity gained from not spreading Ecto calls directly into the business logic cannot be overstated.

Please drop me a note if you end up using BaseModel in something cool, or file an issue if you have difficulty, bugs, or ideas for a better API.