SOLID Principals - Interface Segregation Principle (ISP)
Interface Segregation Principle (ISP) in Ruby: A Practical Guide
The Interface Segregation Principle (ISP) is one of the SOLID principles aimed at guiding object-oriented design. It emphasizes that a class should not be forced to implement interfaces it does not use. In other words, clients should not be forced to depend on interfaces they do not use. In this article, we’ll explore the Interface Segregation Principle through multiple Ruby examples.
Understanding Interface Segregation Principle
ISP suggests that it is better to have many small, specific interfaces tailored for individual classes than a large, general-purpose interface that forces a class to implement methods it doesn’t need. By adhering to ISP, we create more maintainable, flexible, and understandable code.
Example 1: Violation of ISP
Consider a scenario where we have a Worker class that performs both regular work and reports progress:
class Worker
def do_work
# Code to perform general work
end
def report_progress
# Code to report progress
end
end
In this example, the Worker class violates ISP because clients that only need to use the do_work method are forced to deal with the unnecessary report_progress method.
Refactoring for ISP
To adhere to ISP, we can split the interface into two separate interfaces, each catering to a specific set of responsibilities:
module Workable
def do_work
# Code to perform general work
end
end
module ProgressReportable
def report_progress
# Code to report progress
end
end
Now, classes can include the specific modules they need:
class Worker
include Workable
end
class ProgressReporter
include ProgressReportable
end
This adheres to the Interface Segregation Principle by allowing classes to include only the interfaces they require.
Example 2: Applying ISP to Services
Consider a service class that handles both user authentication and file management:
class FileManagementService
def authenticate_user
# Code to authenticate user
end
def upload_file(file)
# Code to upload a file
end
end
In this case, the FileManagementService class has a dual responsibility, violating ISP. Let’s refactor this by creating separate services for authentication and file management:
class AuthenticationService
def authenticate_user
# Code to authenticate user
end
end
class FileManagementService
def upload_file(file)
# Code to upload a file
end
end
Now, we have two classes, each with a single responsibility. This adheres to ISP by allowing clients to depend on specific interfaces without being burdened by unnecessary methods.
Conclusion
The Interface Segregation Principle is about creating focused and specific interfaces tailored to the needs of individual classes. By adhering to ISP, developers can build more modular and maintainable systems. The examples provided demonstrate how to refactor code to follow ISP principles in the context of Ruby, fostering a design that enhances flexibility and reduces dependencies between classes.