Provides functionality similar to Ruby's bitfields
Say you have a user schema that can have one or more of the following service policy [:create_user, :update_user, :delete_user]
To pack that information into a bit we'd do something like this
policies = [create_user: 2^0, update_user: 2^1, delete_user: 2^2]
| create_user | update_user | delete_user | BIT |
|---|---|---|---|
| F | F | F | 0 |
| T | F | F | 1 |
| F | T | F | 2 |
| T | T | F | 3 |
| F | F | T | 4 |
| T | F | T | 5 |
| F | T | T | 6 |
| T | T | T | 7 |
This saves you a couple of migrations and headache and is also is memory efficient.
def deps do
[
{:ecto_bitfield, "~> 0.1.0"}
]
endRun a migration to add a bitfield to the schema
alter table(:users) do
add :policies, :integer, default: 0, null: false
endDefine the Ecto type and use it as the type for the migrated field
defmodule User do
use Ecto.Schema
import EctoBitfield
# takes in a list or a keyword list for explicitly setting the mappings
defbitfield Policies, [:create_user, :update_user, :delete_user]
schema "users" do
field :policies, User.Policies
end
endReading
query = from u in User, where: u.policies == ^[:create_user, :update_user]
#> %Ecto.Queryable{...}
user = Repo.one(query)
#> %User{..., policies: [:create_user, :update_user]}Writing
changeset = Ecto.Changeset.cast(user, %{policies: [:create_user]}, [:policies])
#> %Ecto.Changeset{..., changes: %{policices: 1}}
Repo.update(changeset)
#> {:ok, %User{..., policices: [:create_user]}}