Refactoring Your Rails App with Rails Service Objects

For a Rails controller app, starting with basic models and controllers is advised, but as the app scales up, the models and controllers can grow unwieldy. To combat this, it’s vital to refactor them into Rails service objects which offer a simpler, more manageable codebase.

The importance of Rails service objects

Ruby on Rails service objects follow the Model View Controller (MVC) design pattern, which is ideal for simple and compact solutions. However, as programs become more complex, it’s common for business or domain logic to be scattered across controllers and models, leading to maintenance and reuse challenges. This logic should not be in either the model or the controller and should be tackled to make the codebase more manageable.

Implementing the Rails Service Object Paradigm allows us to extract business logic from models and controllers. This ensures models only serve as data layers while APIs are intended as the controller’s entry point. This separation facilitates a clear understanding of the system’s underlying logic, leading to various benefits. Some of the services we’ve established include:

1. Verifiable controls

   Given that the controllers have minimalistic designs and can work alongside services, the testing process is streamlined. We only need to validate that specific methods in the controller are called when an event happens, which is effortless to accomplish.

2. Leaner Rails controllers

   Controllers are responsible for interpreting incoming requests and converting session and parameter data into a format that service objects can use. The service response decides whether the controller should redirect or render the page. With further scrutiny of complicated applications, you’ll notice that the controller actions that employ Rails services have more code lines.

3. Isolated Domain-Framework

   Using services, controllers in the Ruby on Rails framework can interact with domain objects. This reduces coupling between system components, enhancing scalability, particularly when shifting from a classic monolithic architecture to a microservice architecture. Existing services can be extracted and migrated to a new environment smoothly without requiring any alterations.

4. Reusable Solutions

   Service objects in Rails, also referred to as controllers or queued tasks, function as the “brains” of an application. The controller plays a significant role in improving user engagement with models and views by bridging the gap between incoming requests and the application’s internal entities. Additionally, it is the perfect spot to include vital auxiliary services. Essentially, the controller simplifies the conversion of incoming requests into internal entities.

5. Conducting Independent Business Process Tests

   Services in Ruby are objects that can be tested separately from their environment, making testing much more efficient. This simplifies the process of accurately tracking the time spent by each team member, allowing us to quickly verify adherence to the service’s processes.

Creating Service Objects

1. Our library management program begins with the creation of a new BookCreator in the services/apps folder.
2. Next, we define a new Ruby class and integrate all our logic into it.
3. Finally, we call the service object from the controller or any other part of the application as the third and final step.

Syntactic Sugar for Service Providing Objects

To simplify the BookCreator, we can introduce a class method that generates a new instance and triggers the create function.

We can establish a universal parent that all service objects inherit from, known as the ApplicationService class, which provides an abstract version of the call function. This enables us to avoid redundancy and facilitate the creation of similar service instances in Rails by reusing existing code.

To refactor the BookCreator, we can base it on ApplicationService.

Creating Rails Service Objects with the BusinessProcess Gem

With the BusinessProcess gem, the need for an initialization function or a basic application service class can be eliminated, as it comes with pre-configured settings. The BusinessProcess::Base class serves as the parent class for all service objects.

Actions you can take in your BusinessProcess gem file

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This page outlines the top practices for creating Rails service objects.

1. Ensure that every object in Rails’s service directory has a descriptive name that accurately reflects its function.

   The name of a service object must accurately convey its purpose. It is commonly accepted to name Rails service objects with the suffixes ‘er’ or ‘or.’ For instance, if the service object is designed to create books, a fitting name could be “BookCreator,” whereas if it is intended to read books, “BookReader” might be a suitable name.

2. Single Open Method

   For security reasons, it is important to restrict the exposure of business operations and internal procedures. Service Objects should only have one public method that performs the designated business operation, which should be clearly documented and named in a consistent manner across all Rails Service Objects. The exact implementation of the public method may vary based on developer preference, but the method name must remain consistent.

3. Organise Your Rails Service Objects into Separate Namespaces

   By creating separate namespaces for frequently used Rails service objects, code organization is improved, enabling better scalability for larger applications as additional service objects can be added when requirements change. It is crucial to establish a consistent naming convention for all services linked to books and authors when working with a library application.
   
   Effective immediately, our references to calls will be named Book::BookCreator.call(*args) and Book::BookReader.call(*args).

4. Avoid Directly Instantiating Rails Service Objects

   Using the syntactic sugar pattern and the BusinessProcess gem can be advantageous for simplifying the invocation of Rails service objects. These can help in minimizing complex expressions like BookCreator.new(*args).call or BookCreator.new.call(*args) and make them more concise and easier to understand. This can be achieved by converting them into the more comprehensible BookCreator.call(*args).

5. Use Custom Exceptions to Handle Errors

   The purpose of a service object is to abstract the inner workings of how Rails ActiveRecord interacts with other services, databases, and frameworks. Therefore, the service object should be capable of managing any ActiveRecord-related issues that might occur while preventing a chain reaction of errors. If the error cannot be handled within the rescue block, the service object should throw a custom exception that is specific to its purpose.

6. Single Responsibility Principle for Service Objects

   Service objects in Rails are created to perform a specific task, which is why it is not recommended to create a generalized service object. Instead, if you need to share logic between multiple service objects, you can create a base or helper module and use mixins to incorporate the service into the module. This approach can help reuse logic while retaining the design philosophy of having each service object fulfil a single function.
   
   Implementing the service object design pattern can lend many new functionalities to your application’s design, making it simpler to maintain and more expressive. It can also enhance the testability of the codebase, allowing for easier identification and resolution of any issues.

FAQs

1. What are the Default Environments that Rails Uses?

   Rails comes pre-configured with three environments: test, production, and development. Although references to these environments can be found in the underlying Rails source code, they are standardized and consistent across all applications. This consistency is necessary because the configuration for each environment must be tailored to the specific needs of each application.

2. Is Ruby on Rails Considered a Framework?

   Ruby on Rails is a server-side web application framework written in the Ruby programming language that is released under the MIT Licence. The framework is based on the Model-View-Controller (MVC) architectural pattern, which allows for efficient organization of the codebase while separating the concerns of various web application components, including database logic, web services, and website layout.

3. What is the Difference between a Class and a Module in Ruby?

   Modules are often used to group related constants and procedures together. However, modules cannot independently create new objects; instead, they can be incorporated into other classes and modules of similar types. Constants and methods can be added to a class without interruption, expanding its scope, as there is no parent module to inherit from.
   
   Classes are capable of generating individual objects, each of which has its own unique characteristics, and should not be included in arbitrary contexts. While classes can inherit from other classes, modules do not have this capability.

4. What is the use of hashes in Ruby?

   Ruby hashes are data structures used to store unique key-value pairs. While any type of object may be used as a key for indexing, an array may also be used as a hash. It should be noted, however, that iterating through the set of returned keys and values does not guarantee that they will be returned in the order they were entered, but rather in some defined order.