Welcome back! Now that we’ve covered the basics of controllers in Ruby on Rails, it’s time to dive into another crucial component: services. In the prior lesson, you learned how to create a basic controller, handle HTTP requests, and render JSON responses. Today, we’ll explore how to use services to keep your code organized and maintain a separation of concerns.

Let’s start with understanding why service objects are beneficial. By moving business logic away from controllers and models, services make your codebase more maintainable and easier to test. Services also promote reusability. Instead of writing the same business logic in multiple controllers, you can encapsulate the functionality in a service and call it wherever needed. This makes it easier to ensure consistency across your application. Additionally, services support single responsibility principle (SRP), as each service is focused on a specific aspect of your business logic.

However, this does not mean that you should use services everywhere. Services are not suitable for simple logic easily managed within controllers or models, straightforward database queries best handled by models, or trivial operations that do not significantly benefit from separation of concerns.

While Rails provides generators for common components like controllers, models, and views, there isn't a built-in generator for services. However, you can create a new service file manually or use a custom generator if you prefer. You can create manually by creating a services directory inside the app directory, and create a new service file todo_service.rb.

To illustrate how services work, let's build a simple TodoService. This service will handle fetching a list of to-dos. Remember, keeping these operations in a service makes your controllers neater and your application logic more modular.

Here is the TodoService:

Ruby
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1class TodoService
2  def self.get_todos
3    ['Todo 1', 'Todo 2', 'Todo 3']
4  end
5end

The self keyword in self.get_todos defines get_todos as a class method, allowing it to be called on the class TodoService itself rather than on an instance of the class. This is useful for utility methods that do not depend on instance-specific data.

Now that we've created our service, we can integrate it with a controller to handle a specific action.

Here's the familiar code from last lesson, where TodosController can use the TodoService this time around:

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1class TodosController < ApplicationController
2  def index
3    todos = TodoService.get_todos
4    render json: { todos: todos }
5  end
6end

By using the TodoService, we achieved a clear separation of concerns:

• Controller: Manages web requests and returns appropriate responses.
• Service: Handles business logic and data retrieval.

In this lesson, you learned about the importance of service objects and how they can help you maintain clean and modular code. You also created and integrated a simple TodoService with a controller. Services not only organize your application better but also make it easier to maintain and test.

Now, let's move on to the practice section to solidify your understanding by implementing similar services for other parts of your Todo app. Keep up the great work!