Clean Architecture & Design Patterns in Practice · درس

تصميم كيانات الأعمال

حدّد كائنات الأعمال الأساسية لديك (Entities) التي تغلّف قواعد الأعمال على مستوى المؤسسة وتظل مستقرة.

تصميم كيانات الأعمال درس مجاني في Clean Architecture & Design Patterns in Practice على CoddyKit. هذا هو الدرس 1 من أصل 4. يمكنك قراءة الدرس كاملاً أدناه مجاناً — ثم تمرن عليه مباشرة في المتصفح باستخدام محرر أكواد مدمج ومدرس ذكاء اصطناعي متاح 24/7. هذا الدرس جزء من مسار التعلم في Clean Architecture & Design Patterns in Practice، وتقدمك يتزامن عبر الويب وتطبيق CoddyKit. تتضمن دورة Clean Architecture & Design Patterns in Practice 4 دروس في المجموع.

بعض أجزاء هذا الدرس لم تُترجم بعد وتظهر باللغة الإنجليزية.

What are Business Entities?

In Clean Architecture, Entities are the heart of your application. They represent the core business concepts and rules that are crucial to your enterprise.

Think of them as the fundamental building blocks that define "what your business is" and "how it works," independent of how you store or display data.

Core Business Rules

Entities encapsulate enterprise-wide business rules. These are rules that would exist even if there were no software system, like "a product must have a positive price" or "an order must have a customer."

These rules are stable and apply across your entire organization, not just a specific part of your application.

Independent & Stable

A key principle of Entities is their independence. They should not depend on external layers like databases, web frameworks, or UI components.

This makes them the most stable part of your application, changing only when the core business rules themselves change, not when technology does.

Entity vs. DTO

It's important to distinguish an Entity from a simple Data Transfer Object (DTO). A DTO is just a bag of data, often used to move data between layers.

An Entity, however, contains both data and behavior. It actively enforces its own business rules through its methods.

Entity Structure

Typically, an Entity includes:

Attributes: The data that describes the business object (e.g., name, ID, price).
Methods: The operations that can be performed on the entity, enforcing its business rules and maintaining its integrity.

These methods ensure the entity always remains in a valid state according to your business logic.

Example: `Product` Entity

Let's consider a simple Product entity. What data and rules would it need?

A product needs an id, name, and price.
A core business rule might be: "A product's price must always be positive."

The entity itself should enforce this rule.

`Product` Entity Code

Here's how a basic Product entity might look in Java, ensuring the price rule:

public class Product {
  private String id;
  private String name;
  private double price;

  public Product(String id, String name, double price) {
    if (price <= 0) {
      throw new IllegalArgumentException("Price must be positive.");
    }
    this.id = id;
    this.name = name;
    this.price = price;
  }

  public String getId() { return id; }
  public String getName() { return name; }
  public double getPrice() { return price; }

  public static void main(String[] args) {
    try {
      Product laptop = new Product("P001", "Laptop", 1200.00);
      System.out.println(laptop.getName() + " costs $" + laptop.getPrice());
      // This would throw an error:
      // Product invalid = new Product("P002", "Free Item", 0.00);
    } catch (IllegalArgumentException e) {
      System.out.println("Error creating product: " + e.getMessage());
    }
  }
}

Entity Behavior & Rules

Entities aren't just data containers; they have methods that encapsulate behavior and enforce rules. For example, applying a discount might have its own business logic.

The entity's methods ensure its internal state remains consistent and valid according to business rules.

`Product` Discount Example

Let's add a method to our Product entity to apply a discount, with a rule that discounts can't make the price negative.

public class Product {
  private String id;
  private String name;
  private double price;

  public Product(String id, String name, double price) {
    if (price <= 0) {
      throw new IllegalArgumentException("Price must be positive.");
    }
    this.id = id;
    this.name = name;
    this.price = price;
  }

  public String getId() { return id; }
  public String getName() { return name; }
  public double getPrice() { return price; }

  // New method to apply discount
  public void applyDiscount(double percentage) {
    if (percentage < 0 || percentage > 100) {
      throw new IllegalArgumentException("Discount must be between 0-100%.");
    }
    double newPrice = this.price * (1 - percentage / 100);
    if (newPrice < 0) { // Ensure price doesn't go negative
      this.price = 0;
    } else {
      this.price = newPrice;
    }
  }

  public static void main(String[] args) {
    Product book = new Product("B001", "Clean Code Book", 40.00);
    System.out.println("Original: " + book.getName() + " $" + book.getPrice());
    book.applyDiscount(25); // 25% discount
    System.out.println("Discounted: " + book.getName() + " $" + book.getPrice());

    try {
      book.applyDiscount(150); // Invalid discount
    } catch (IllegalArgumentException e) {
      System.out.println("Error applying discount: " + e.getMessage());
    }
  }
}

Entity Properties Check

Based on what we've learned, which of the following are true characteristics of a Clean Architecture Entity?

Recap: Designing Entities

Great job! You've learned about Entities in Clean Architecture. Key takeaways:

Entities represent your core business concepts.
They encapsulate enterprise-wide business rules.
Entities contain both data and behavior, actively enforcing their rules.
They are independent and stable, not tied to frameworks or external layers.

Next, we'll explore how Use Cases interact with these robust entities to perform application-specific tasks.

الأسئلة الشائعة

هل درس «تصميم كيانات الأعمال» مجاني؟

نعم — نص درس «تصميم كيانات الأعمال» كامل متاح مجاناً هنا على الويب. لتمرينه بشكل تفاعلي (محرر أكواد مدمج ومدرس ذكاء اصطناعي متاح 24/7) وفتح باقي دورة Clean Architecture & Design Patterns in Practice، انتقل إلى CoddyKit PRO. تتضمن دورة Clean Architecture & Design Patterns in Practice 4 دروس في المجموع.

ماذا ستتعلم في «تصميم كيانات الأعمال»؟

حدّد كائنات الأعمال الأساسية لديك (Entities) التي تغلّف قواعد الأعمال على مستوى المؤسسة وتظل مستقرة. تتمرن على Clean Architecture & Design Patterns in Practice مع أكواد عملية تشغلها مباشرة في المتصفح، ومدرس ذكاء اصطناعي متاح 24/7 يجيب على أسئلتك أثناء عملك.

هل أحتاج إلى خبرة سابقة لأبدأ Clean Architecture & Design Patterns in Practice؟

لا تُشترط خبرة سابقة. Clean Architecture & Design Patterns in Practice على CoddyKit منظم للمبتدئين حتى المتقدمين، لذا يمكنك البدء من هنا أو من البداية والتقدم بسرعتك الخاصة. هذا هو الدرس 1 من أصل 4.

كم من الوقت يستغرق درس «تصميم كيانات الأعمال»؟

معظم دروس CoddyKit تستغرق حوالي 5–10 دقائق. كل منها موجز وتفاعلي، لذا تحرز تقدماً مستمراً وتستأنف من حيث توقفت عبر الويب والتطبيق.

هل يمكنني كتابة وتشغيل أكواد في درس Clean Architecture & Design Patterns in Practice هذا؟

نعم. كل درس في Clean Architecture & Design Patterns in Practice يتضمن محرر أكواد مدمج، لذا تكتب وتشغل أكواداً حقيقية مباشرة في متصفحك وتحصل على تعليقات فورية من الذكاء الاصطناعي — بدون إعداد محلي.

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