How does the repository pattern abstract away the specific technical details of exactly where data actually comes from, such as a remote API versus a local cache, from the rest of an app's business logic?

A repository defines an abstract interface describing what specific data operations are actually available, such as fetching a list of products or saving a specific user's completed order, while its own concrete internal implementation handles the genuine technical details of exactly where that data actually comes from, whether that means a live remote API call, a locally cached database query, or potentially some combination of both, and the rest of your app's own business logic only ever needs to depend on that abstract repository interface itself, meaning the underlying data source implementation can later be freely and easily changed, such as adding local caching, without requiring any change whatsoever to the actual business logic that genuinely depends on it.

abstract class ProductRepository {
  Future<List<Product>> getProducts();
}

class ApiProductRepository implements ProductRepository {
  @override
  Future<List<Product>> getProducts() => apiClient.fetchProducts();
}