Should DTOs inherit?
The “one DTO class” approach is almost certainly bad. It smells like a God Class. Many pundits excoriate DTOs altogether. You could inherit from some base class, but for value objects it’s not really sensible.
When should we use composition and why it is better than inheritance?
Prefer composition over inheritance as it is more malleable / easy to modify later, but do not use a compose-always approach. With composition, it’s easy to change behavior on the fly with Dependency Injection / Setters. Inheritance is more rigid as most languages do not allow you to derive from more than one type.
What is composition and inheritance Javascript?
Using the Composition pattern, you design your models for what they can do, while using inheritance pattern, you create your models for what they are. Inheritance is more rigid, and the objects usually will finish with a lot of functionality that they don’t use.
How do you implement composition over inheritance?
An implementation of composition over inheritance typically begins with the creation of various interfaces representing the behaviors that the system must exhibit. Interfaces enable polymorphic behavior. Classes implementing the identified interfaces are built and added to business domain classes as needed.
Is it bad to use composition in DTOs?
Using composition in DTOs is a perfectly fine practice. Inheritance among concrete types of DTOs is a bad practice. For one thing, in a language like C#, an auto-implemented property has very little maintainability overhead so duplicating them (I truly abhor duplication) is not as harmful as it oftentimes is.
Why is concrete inheritance not used in DTOs?
For one thing, in a language like C#, an auto-implemented property has very little maintainability overhead so duplicating them (I truly abhor duplication) is not as harmful as it oftentimes is. One reason not to use concrete inheritance among DTOs is that certain tools will happily map them to the wrong types.
When to use composition over inheritance in Python?
Use composition over inheritance in Python to create components that can be reused by multiple classes in your Python applications. Use composition over inheritance in Python to implement groups of behaviors and policies that can be applied interchangeably to other classes to customize their behavior.
Do you have a DTO class for each entity?
I think it feels a bit superfluous. Recommendation is that you should just have one DTO class for each entity suffixed with DTO e.g. CustomerEntryDTO for the Customer entity (but you can certainly use inheritance hierarchies as per choice and requirements).