Active Record vs Data Mapper

    Using the Active Record approach, you define all your query methods inside the model itself, and you save, remove, and load objects using model methods.

    Simply said, the Active Record pattern is an approach to access your database within your models.You can read more about the Active Record pattern on .

    Example:

    All active-record entities must extend the class, which provides methods to work with the entity.Example of how to work with such entity:

    2. // example how to save AR entity
    3. const user = new User();
    4. user.firstName = "Timber";
    5. user.lastName = "Saw";
    6. user.isActive = true;
    8. // example how to remove AR entity
    9. await user.remove();
    11. // example how to load AR entities
    12. const users = await User.find({ skip: 2, take: 5 });
    14. const timber = await User.findOne({ firstName: "Timber", lastName: "Saw" });

    BaseEntity has most of the methods of the standard Repository.Most of the time you don’t need to use Repository or EntityManager with active record entities.

    And use it just like other methods:

    1. const timber = await User.findByName("Timber", "Saw");

    In TypeORM you can use both the Active Record and Data Mapper patterns.

    Using the Data Mapper approach, you define all your query methods in separate classes called “repositories”,and you save, remove, and load objects using repositories.In data mapper your entities are very dumb - they just define their properties and may have some “dummy” methods.

    Simply said, data mapper is an approach to access your database within repositories instead of models.You can read more about data mapper on Wikipedia.

    Example:

    1. const userRepository = connection.getRepository(User);
    3. // example how to save DM entity
    4. user.firstName = "Timber";
    5. user.lastName = "Saw";
    7. await userRepository.save(user);
    9. // example how to remove DM entity
    10. await userRepository.remove(user);
    12. // example how to load DM entities
    13. const users = await userRepository.find({ skip: 2, take: 5 });
    14. const newUsers = await userRepository.find({ isActive: true });
    15. const timber = await userRepository.findOne({ firstName: "Timber", lastName: "Saw" });

    Now let’s say we want to create a function that returns users by first and last name.We can create such a function in a “custom repository”.

    And use it this way:

    1. const timber = await userRepository.findByName("Timber", "Saw");

    Learn more about .

    The decision is up to you.Both strategies have their own cons and pros.

    One thing we should always keep in mind in with software development is how we are going to maintain our applications.The Data Mapper approach helps with maintainability, which is more effective in bigger apps.The Active record approach helps keep things simple which works well in smaller apps. And simplicity is always a key to better maintainability.