Collection vs Repository

[Toonvd]

In the student guide I read that a collection returns a list of models and Repositories provide high level access to data. When I read this, I conclude that I should always return data and not models. In the core (several sales repos) I see returns of several models. Am I understanding this concept wrong or are there "possible exceptions"?

[akent99 · Accepted solution]

There are service contracts like https://github.com/magento/magento2/blob/develop/app/code/Magento/Customer/Api/CustomerRepositoryInt... - it is the external API for accessing a "repository". If you implement such a contract you should return data structures that implement the interfaces defined there. Those implementations will probably be classes (models), but could be just a separate class holding the data. As long as you implement the interface, the caller *should* not care. (People take short cuts!) Searches return things like \Magento\Customer\Api\Data\CustomerSearchResultsInterface at this level.

Collection is defined in Magento\Framework\Data\Collection (e.g. https://github.com/magento/magento2/blob/develop/lib/internal/Magento/Framework/Data/Collection.php)... is not part of the repository interface. It is a more low level API to access the database.

So a module frequently uses a collection to implement repository based service contracts.