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The repository pattern is one of the more fundamental differences between LoopBack 3 and 4. In LoopBack 3, you would use the model class definitions themselves to perform CRUD operations. In LoopBack 4, the layer responsible for this has been separated from the definition of the model itself, into the repository layer.

A Repository represents a specialized Service interface that provides strong-typed data access (for example, CRUD) operations of a domain model against the underlying database or service.

For more information about Repositories, see Repositories.

Create your repository

From inside the project folder, run the lb4 repository command to create a repository for your to-do model using the db datasource from the previous step. The db datasource shows up by its class name DbDataSource from the list of available datasources.

lb4 repository
? Please select the datasource DbDatasource
? Select the model(s) you want to generate a repository Todo
? Please select the repository base class DefaultCrudRepository (Juggler bridge)

   create src/repositories/todo.repository.ts
   update src/repositories/index.ts

Repository TodoRepository was created in src/repositories/

The src/repositories/index.ts file makes exporting artifacts central and also easier to import.

The newly created todo.repository.ts class has the necessary connections that are needed to perform CRUD operations for our to-do model. It leverages the Todo model definition and ‘db’ datasource configuration and retrieves the datasource using Dependency Injection.

To view the completed file, see the Todo example.

Now we can expose the Todo API through the controller.

Previous step: Add a datasource

Next step: Add a controller