In Clean Architecture, the distinction between Request/Response Models and Entities is crucial for maintaining a clear separation of concerns and ensuring the flexibility and maintainability of the software system.
Entities
Entities are core domain objects that encapsulate business logic and represent the fundamental concepts and rules of the problem domain. They are designed to be independent of any specific use case, framework, or external system. Entities are typically pure data structures that contain both data and behavior relevant to the business logic. They are central to the domain layer and are meant to be stable and reusable across different parts of the application.
For example, an entity might look like this in TypeScript:
class Product {
constructor(
public id: number,
public name: string,
public description: string,
public price: number,
public available: boolean
) {}
canBePurchased(): boolean {
return this.available && this.price > 0;
}
}
Request/Response Models
Request and Response Models, on the other hand, are used to facilitate communication between different layers of the application, particularly between the user interface and the business logic. These models are designed to represent the state of the system at a particular point in time and are often tailored to the specific needs of a use case or an external system. They serve as data transfer objects (DTOs) that carry data between the layers without containing any business logic.
For instance, a request model might be used to capture input data from a user interface, while a response model might be used to format data for presentation to the user. These models are typically defined in the application layer and are mapped to and from entities as needed.
Here is an example of mapping between an entity and a data model in TypeScript:
// Entity
class User {
constructor(public id: number, public name: string, public email: string) {}
}
// Model
class UserDataModel {
constructor(public id: number, public username: string, public emailAddress: string) {}
}
// Mapping function
function mapDataModelToEntity(dataModel: UserDataModel): User {
return new User(dataModel.id, dataModel.username, dataModel.emailAddress);
}
Key Differences
Purpose:
Entities: Encapsulate business logic and represent core domain concepts.
Request/Response Models: Facilitate data transfer between layers and external systems.
