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defmodule Amodel do | |
use Ecto.Schema | |
import Estate, only: [machine: 1] | |
machine([ | |
onboarding_state: [ | |
complete: [converted: "completed"] | |
], | |
role_state: [ | |
grant_moderation_powers: [user: "moderator"], | |
grant_administrator_powers: [user: "administrator", moderator: "administrator"] | |
] | |
]) | |
end |
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defmodule Estate do | |
defmacro machine(machines) do | |
Enum.flat_map(machines, fn ({column_name, events}) -> | |
Enum.flat_map(events, fn ({event_name, transitions}) -> | |
Enum.map(transitions, fn ({from, to}) -> | |
quote do | |
@desc "A before hook" | |
def unquote(:"before_#{event_name}")(%Ecto.Changeset{} = record) do | |
record | |
end | |
@desc "An after hook" | |
def unquote(:"after_#{event_name}")(%{} = record) do | |
record | |
end | |
@desc "An action to change the state, if the transition matches, but doesn't save" | |
def unquote(event_name)(%{unquote(column_name) => unquote(Atom.to_string(from))} = record) do | |
record | |
|> Ecto.Changeset.change() | |
|> unquote(:"before_#{event_name}")() | |
|> Ecto.Changeset.cast(%{unquote(column_name) => unquote(to)}, [unquote(column_name)]) | |
|> Ecto.Changeset.validate_required(unquote(column_name)) | |
|> unquote(:"after_#{event_name}")() | |
end | |
@desc "An action to change the state, if the transition matches, but does save" | |
def unquote(:"#{event_name}!")(%{:id => id, unquote(column_name) => unquote(Atom.to_string(from))} = record) when not is_nil(id) do | |
record | |
|> Ecto.Changeset.change() | |
|> unquote(:"before_#{event_name}")() | |
|> Ecto.Changeset.cast(%{unquote(column_name) => unquote(to)}, [unquote(column_name)]) | |
|> Ecto.Changeset.validate_required(unquote(column_name)) | |
|> Poutineer.Repo.update() | |
|> unquote(:"after_#{event_name}")() | |
end | |
# If you can't match, then raise transition failure | |
end | |
end) | |
end) | |
end) | |
end | |
end |
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