Domain Modeling

• Why? - Learn how Value Objects are used to effectively model domain concepts and represent real-world entities in code. README.md
• How? - Value Objects provide a way to represent strongly typed domain objects that are immutable, providing several benefits. README.md

Value Objects

• Define: A strongly typed (strongly, not stringly) domain object that is immutable. README.md
• Implementation:
  • Instead of using primitives such as int, Value Objects are used. README.md
  • Derived from the ValueObject type. README.md
  • Example: README.md

  public class CustomerId : ValueObject
            {
            }
            

Value Object Validation

• Why? - Enforces constraints on Value Objects, ensuring they are valid and meet domain requirements. README.md
• Implementation:
  • Validate() method defined in the derived Value Object class. README.md
  • Example: README.md

  public class CustomerId : ValueObject
            {
                public override Validation Validate() => Value > 0
                ? Validation.Ok
                : Validation.Invalid("Customer IDs cannot be zero or negative.");
            }
            

• Benefits:
  • Ensures validity: Guarantees that Value Objects are valid before they are used. README.md
  • Single point of validation: Validation logic is centralized in one place. README.md

Primitive Obsession

• Definition: Using primitive data types to represent domain ideas, which can lead to issues like improper validation, lack of type safety, and difficulty in representing complex domain concepts. README.md
• Code Smell: “Primitive Obsession is using primitive data types to represent domain ideas” README.md
• Example: README.md

  int customerId = 42
            

• Issues:
  • No constraints: Primitive types lack the ability to enforce domain-specific constraints. README.md
  • Type safety issues: Primitives offer less type safety compared to Value Objects. README.md

Benefits of Using Value Objects

• Type Safety: Value Objects enhance type safety, preventing accidental misuse of data. README.md
• Improved Code Readability: Code becomes more readable by using dedicated types for domain concepts. README.md
• Reduced Errors: Value Objects help reduce the risk of errors by enforcing validation and immutability. README.md
• Encapsulation: Value Objects encapsulate data and behavior related to a domain concept. README.md

Examples

• Method Signature: README.md
  • Primitive type example:

    public void DoSomething(int customerId, int supplierId, int amount)
              

  • Value Object example:

    public void DoSomething(CustomerId customerId, SupplierId supplierId, Amount amount)
              

• Object Creation: README.md
  • Primitive type example:

    int customerId = 42;
              

  • Value Object example:

    var customerId = CustomerId.From(42);
              

Additional Resources

• For an alternative, more performant approach to Value Objects, please see https://github.com/SteveDunn/Vogen README.md

          ## Top-Level Directory Explanations
          
          <a class='local-link directory-link' data-ref="samples/" href="#samples/">samples/</a> - This directory contains example projects demonstrating the usage of StringlyTyped library.
          
          <a class='local-link directory-link' data-ref="src/" href="#src/">src/</a> - This directory contains the source code of the StringlyTyped library.
          
          <a class='local-link directory-link' data-ref="tests/" href="#tests/">tests/</a> - This directory contains unit tests for the StringlyTyped library. It includes benchmark tests and small tests.