Ecto v0.4.0 → Overview → Ecto → Model → Callbacks

Ecto.Model.Callbacks

Define module-level callbacks in models.

A callback is invoked by your Ecto.Repo before (or after) particular events. A callback must always return the given module and they always run inside a transaction.

Example

defmodule User do
  use Ecto.Model.Callbacks

  after_create Stats, :increase_user_count

  def increase_user_count(user)    # ...  endend

When creating the user, the after_create callbacks will be invoked with the user struct as argument. Multiple callbacks can be defined, they will be invoked in order of declaration.

Usage

Callbacks in Ecto are useful for data consistency, for keeping counters, setting fields and so on. Avoid using callbacks for business rules or doing actions unrelated to the data itself, like sending e-mails.

Finally, keep in mind callbacks are not invoked on bulk actions such as Repo.delete_all or Repo.update_all.

Source

Summary↑

__apply__(model, callback)

Applies stored callbacks to a model
after_delete(module, function)

Adds a callback to the model that is invoked before the model is deleted from the database
after_insert(module, function)

Adds a callback to the model that is invoked after the model is inserted into the database
after_update(module, function)

Adds a callback to the model that is invoked after the model is updated
before_delete(module, function)

Adds a callback to the model that is invoked before the model is deleted from the database
before_insert(module, function)

Adds a callback to the model that is invoked before the model is inserted into the database
before_update(module, function)

Adds a callback to the model that is invoked before the model is updated

Functions

__apply__(model, callback)
(function) # ↑

Applies stored callbacks to a model.

Checks wether the callback is defined on the model, returns the model unchanged if it isn't.

Examples

iex> Ecto.Model.Callbacks.__apply__ %User{}, :before_create
%User{some_var: "has changed"}
Source

Macros

after_delete(module, function)
(macro) # ↑

Adds a callback to the model that is invoked before the model is deleted from the database.

Takes the module and the function that are to be invoked as parameters.

Example

after_delete UserMailer, :send_questioneer
Source
after_insert(module, function)
(macro) # ↑

Adds a callback to the model that is invoked after the model is inserted into the database.

Takes the module and the function that are to be invoked as parameters.

Example

after_insert Stats, :increase_user_count
Source
after_update(module, function)
(macro) # ↑

Adds a callback to the model that is invoked after the model is updated.

Takes the module and the function that are to be invoked as parameters.

Example

after_update User, :notify_account_change
Source
before_delete(module, function)
(macro) # ↑

Adds a callback to the model that is invoked before the model is deleted from the database.

Takes the module and the function that are to be invoked as parameters.

Example

before_delete User, :copy_to_archive
Source
before_insert(module, function)
(macro) # ↑

Adds a callback to the model that is invoked before the model is inserted into the database.

Takes the module and the function that are to be invoked as parameters.

Example

before_insert User, :generate_permalink
Source
before_update(module, function)
(macro) # ↑

Adds a callback to the model that is invoked before the model is updated.

Takes the module and the function that are to be invoked as parameters.

Example

beforeupdate User, :setupdateattimestamp

Source