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# What are Filters and callbacks in rails?

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In Ruby on Rails, filters and callbacks are mechanisms that allow you to run specific methods at particular points in the lifecycle of a request or an object. Here’s a breakdown of each:

Filters
Filters are used in controllers to run methods before, after, or around a controller action. They are typically used for tasks like authentication, logging, or setting up variables.
  • before_action: Runs a method before the controller action.
  • after_action: Runs a method after the controller action.
  • around_action: Runs a method both before and after the controller action.
Example:

class ApplicationController < ActionController::Base
  before_action :authenticate_user

  private

  def authenticate_user
    # Logic to authenticate user
  end
end

Callbacks

Callbacks are used in models to trigger logic before or after an alteration of an object’s state. They are useful for tasks like data validation, normalization, or logging.
  • before_validation: Runs before validation.
  • after_validation: Runs after validation.
  • before_save: Runs before saving the object.
  • after_save: Runs after saving the object.
  • before_create: Runs before creating a new object.
  • after_create: Runs after creating a new object.
  • before_update: Runs before updating an object.
  • after_update: Runs after updating an object.
  • before_destroy: Runs before destroying an object.
  • after_destroy: Runs after destroying an object.
Example:

class User < ApplicationRecord
  before_save :normalize_name

  private

  def normalize_name
    self.name = name.downcase.titleize
  end
end
These mechanisms help in keeping your code organized and maintainable by separating concerns and ensuring that certain actions are performed at the right time.