Welcome back! In this lesson, we will explore how to set up a POST request in a Ruby on Rails ToDo application to create new ToDo items. This marks an essential step in building our RESTful API, enabling users to add new tasks to their ToDo lists.

By the end of this lesson, you will be able to create a new ToDo item using a POST request. This skill will allow your application to handle new data input from users, making it interactive and dynamic. Let's get started!

The TodosController is responsible for handling requests related to ToDo items. In this lesson, we will focus on setting up the create action within this controller to enable the creation of new ToDo items.

Below is the code required to set up the TodosController:

Ruby
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1# app/controllers/todos_controller.rb
2class TodosController < ApplicationController
3  def create
4    todo = TodoService.create(todo_params)
5    render json: todo, status: :created
6  end
7
8  private
9
10  def todo_params
11    params.require(:todo).permit(:title, :description)
12  end
13end

Explanation:

• create action: This action receives the incoming POST request, invokes the TodoService.create method to handle the creation of a new ToDo item, and then renders a JSON response with the created item and a created status. As mentioned previously, Rails automatically links the POST request on /todos to the create action in the TodosController.
• todo_params: This private method ensures only the permitted parameters (title and description) are passed to the model, protecting against unwanted data. In Rails, such strong parameters help prevent unwanted data from entering our database by ensuring only allowed attributes are passed through the controller actions. This provides a layer of security and data integrity:
  • params.require(:todo): Ensures that the parameters sent with the request contains a todo object.
  • permit(:title, :description): Specifies the attributes that are allowed within the todo object, filtering out any other input.

By using strong parameters, we enforce strict criteria on incoming data, enhancing the security and reliability of our application.

To keep our code modular and maintainable, we delegate the business logic for creating ToDo items to the service class TodoService. This separation of concerns is a standard best practice in Rails applications.

Here is how we implement the TodoService.create method:

Ruby
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1# app/services/todo_service.rb
2class TodoService
3  def self.create(params)
4    todo = { id: @todos.size + 1, **todo_params }
5    @todos << todo
6    todo
7  end
8end

Explanation:

• todo = { id: @todos.size + 1, **todo_params }: This line creates a new ToDo item with a unique ID based on the current size of the @todos array and the provided parameters.
• @todos << todo: The newly created ToDo item is added to the @todos array.
• todo: The new ToDo item is returned.

This approach makes our TodosController more concise and focused purely on handling HTTP requests and responses.

After creating a new ToDo item, we need to provide feedback to the client indicating that the operation was successful. We do this using the render method in our create action:

Ruby
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1def create
2  todo = TodoService.create(todo_params)
3  render json: todo, status: :created
4end

Explanation:

• render json: todo: Converts the ToDo object to JSON format, making it suitable for API responses.
• status: :created: Sets the HTTP status code to 201 Created, indicating that a new resource was successfully created.

By providing a clear JSON response and an appropriate status code, we ensure that clients interacting with our API receive meaningful feedback.

In this lesson, we covered the critical steps needed to set up a creation query for adding ToDo items in a Ruby on Rails application. We:

• Introduced the TodosController and the create action.
• Explained the role of strong parameters and implemented the todo_params method.
• Connected the controller to the TodoService to handle the business logic.
• Discussed response handling and the importance of appropriate status codes.

As we move forward, you’ll get the chance to apply what you’ve learned in practice exercises. These exercises will help reinforce the concepts and ensure you are comfortable creating and managing POST requests in a Rails application.

Keep up the excellent work, and let's continue building our ToDo app!