Written by Armakuni

Sep 17, 2024

Demystifying Event-Driven Architectures and Event Sourcing: Key Differences and Synergies

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If you’re transitioning to a programming language like Python or TypeScript that supports multiple paradigms but come from an object-oriented programming (OOP) background, you might prefer sticking with OOP practices. While using classes is entirely valid, you may end up creating unnecessary boilerplate code. Here’s how you can simplify common single-method class patterns by using functions, reducing boilerplate and enhancing code clarity.

Simplifying Single-Method Classes

Single-method classes are designed to represent a specific action, often wrapping state or dependencies needed for the method’s execution. Here’s how you can simplify these classes.

Refactoring Simple Actions

The simplest case involves a class that only wraps a function without any dependencies. For instance, a class that performs addition can be simplified:

Class-Based Approach:

python

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class Adder: def calculate(self, a: int, b: int) -> int: return a + b

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Function-Based Approach:

python

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def add(a: int, b: int) -> int: return a + b

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While you lose the interface implementation with a function, you can use type aliases to define callable types for abstraction:

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Calculator = Callable[[int, int], int]

Simplifying Dependency Injection

Another example is a class that uses constructor injection to manage dependencies:

Class-Based Approach:

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class OrderCreator: def __init__(self, order_repository: OrderRepository, email_sender: EmailSender): self._order_repository = order_repository self._email_sender = email_sender def create_order(self, customer: Customer, items: list[Items]) -> None: order_id = OrderID.generate() order = Order(order_id, items) self._order_repository.save(order) confirmation_email = Email(to=customer, subject=f"Thank you for your order {order_id}") self._email_sender.send(confirmation_email)

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Function-Based Approach:

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CreateOrder = Callable[[Customer, list[Items]], None] def new_order_creator(order_repository: OrderRepository, email_sender: EmailSender) -> CreateOrder: def create_order(customer: Customer, items: list[Items]) -> None: order_id = OrderID.generate() order = Order(order_id, items) order_repository.save(order) confirmation_email = Email(to=customer, subject=f"We have received your order {order_id}") email_sender.send(confirmation_email) return create_order

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Handling Deferred Dependencies

A similar simplification applies when using deferred dependencies:

Class-Based Approach:

python

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class Email: def __init__(self, to: str, subject: str, body: str): self._to = to self._subject = subject self._body = body def send(self, sender: EmailSender) -> None: sender.send(self._to, self._subject, self._body)

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Function-Based Approach:

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SendEmail = Callable[[EmailSender], None] def create_email(to: str, subject: str, body: str) -> SendEmail: def send(sender: EmailSender) -> None: sender.send(to, subject, body) return send

Summary

For classes with a single method, consider using functions to streamline your code. While this approach may seem to move away from OOP, it retains the concept of encapsulating behavior while reducing boilerplate. Type aliases can offer named abstractions for these functions, maintaining clarity and improving communication. In object-oriented languages, command classes might still be necessary, but in multi-paradigm languages, functions often provide a more concise and readable alternative.

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