How to avoid callbacks using services.
Often, programmers abuse callbacks, not fully understanding that their code will ultimately be confusing and non-obvious. There are several ways to avoid using callbacks. Today, I will tell you how to do this using services.
Let’s see on a code:
class User < ApplicationController
def create
@user = User.new(user_params)
if @user.save
redirect_to root_path, notice: "User created!"
else
render :new, error: 'Failed to create user!'
end
end
end
class User < ApplicationRecord
before_create :populate_serial_number
private
def populate_serial_number
self.serial_number ||= SecureRandom.uuid
end
end
What is the problem with this code?
We get a non-obvious (magical) action. We do not pass any data about the serial number in the parameters or explicitly set this value anywhere. This happens automatically with a callback.
Let’s implement the same thing but using a service.
class CreateUser
def self.call(params)
@user = User.new(params)
populate_serial_number(@user)
# Other actions for the user
user.save!
end
def self.populate_serial_number(user)
user.serial_number ||= SecureRandom.uuid
end
end
class User < ApplicationRecord
end
class User < ApplicationController
def create
@user = CreateUser.call(user_params)
if @user
redirect_to root_path, notice: "User created!"
else
render :new, error: 'Failed to create user!'
end
end
def user_params
...
end
end
What advantages does this approach give us?
Suppose we have users that can be created from the Admin panel and through the API. Depending on the creation method, we may perform different actions on the user. It is very convenient to create two separate services for creating a user. For example: Admin::CreateUser
and Api::CreateUser
- Such services are accessible to test.
- They are easy to expand.
- The code becomes much more transparent and more predictable.