Can you explain the concept and purpose of the repository pattern in software development?

The repository pattern is an abstraction layer between the application's business logic and the data source (e.g., a database). It encapsulates data access logic, providing a convenient interface for retrieving, adding, updating, and deleting objects.

Purpose of the pattern:

• Hide the details of working with the database or other storage.
• Provide a unified interface for data operations.
• Simplify testing by allowing the repository to be replaced with mocks.

Example in Kotlin for Android:

interface UserRepository {
    fun getUserById(id: Int): User?
    fun addUser(user: User)
}

class UserRepositoryImpl(private val userDao: UserDao) : UserRepository {
    override fun getUserById(id: Int): User? = userDao.findById(id)
    override fun addUser(user: User) = userDao.insert(user)
}

Here, UserRepository hides the details of working with UserDao (e.g., Room), providing a simple interface for the rest of the application.