Use UseCase to execute operation by following SRP.

AndroidTips5.kt

/**
 * UseCase is designed to execute a given operation by following
 * Single Responsibility Design Principle.
 */
abstract class UseCaseV2<ReturnType, in Params> where ReturnType : Any {
    /**
     * Abstract API that should be implemented by the respective child to execute the operation.
     *
     * @param params [Params]
     *
     * @return [AppResult]<[ReturnType]>
     */
    abstract suspend fun run(params: Params): AppResult<ReturnType>

    /**
     * Client access point to execute the [UseCaseV2].
     *
     * Can provide [CoroutineDispatcher] to execute the [UseCaseV2]
     * with the context of provided [CoroutineDispatcher].
     *
     * Also, client can define that if this [UseCaseV2] is performing
     * CPU intensive work or not. If yes, use [Dispatchers.Default]
     * else accept the execution as IO Operation and use [Dispatchers.IO].
     *
     * Note: [isCPUIntensiveWork] will work only if [useCustomDispatcher] is null.
     *
     * @param params [Params] to be passed.
     * @param useCustomDispatcher to execute [UseCaseV2] with provided [CoroutineDispatcher] context.
     * @param isCPUIntensiveWork to execute [UseCaseV2] with [Dispatchers.Default] if true else [Dispatchers.IO]
     *
     * @return [AppResult]<[ReturnType]>
     */
    suspend operator fun invoke(
        params: Params,
        useCustomDispatcher: CoroutineDispatcher? = null,
        isCPUIntensiveWork: Boolean = false
    ): AppResult<ReturnType> {
        val dispatcher = useCustomDispatcher
            ?: if (isCPUIntensiveWork)
                Dispatchers.Default
            else
                Dispatchers.IO
        return withContext(dispatcher) { run(params) }
    }
}

interface AuthRepo {
    fun login(username: String, password: String): AppResult<String>
}

class AuthRepoImpl() : AuthRepo {
    override fun login(username: String, password: String): AppResult<String> {
        //Assume that we are doing some kind of network operations here.
        return AppResult.Success("Login Success.")
    }
}

class LoginUseCase(private val repo: AuthRepo) : UseCaseV2<String, Pair<String, String>>() {
    override suspend fun run(params: Pair<String, String>): AppResult<String> =
        repo.login(params.first, params.second)
}

class AuthViewModel() : ViewModel() {
    private val loginUseCase = LoginUseCase(AuthRepoImpl())

    suspend fun login(username: String, password: String) = loginUseCase(
        Pair(username, password), null, false
    )
}