Using sealed classes for intents.

[nicbell]

Hey

I have a proposal to switch to using sealed classes, data classes and objects to represent intents.

Currently we are exposing multiple functions from our view models to our views to represent actions

class MyLoginViewModel : AndroidDataFlow()
  fun login(mobileNumber: String, code: String) = action { 
    // Manipulate state
  }
  
  fun resendCode(mobileNumber: String) = action { 
   // Manipulate state
  }
}

// In our view
viewModel.login(mobileNumber, code)
viewModel.resendCode(mobileNumber)

Recently in projects I have been using this approach to have fewer public functions and use sealed classes for intents and handle the intents in an exhaustive way.

sealed class MyLoginIntent {
  data class Login(mobileNumber: String, code: String) : MyLoginIntent()
  data class ResendCode(mobileNumber: String) : MyLoginIntent()
}

class MyLoginViewModel : AndroidDataFlow()
  fun onAction(intent: MyLoginIntent) = action {
    when(intent) {
      is MyLoginIntent.Login -> login(intent)
      is MyLoginIntent.ResendCode -> resendCode(intent)
    }  
  }
  
  private suspend fun login(loginIntent: MyLoginIntent.Login) { 
     // Manipulate state
  }

  private suspend fun resendCode(resendCodeIntent: MyLoginIntent.ResendCode) {  
     // Manipulate state
  }
}

// In our view
viewModel.onAction(MyLoginIntent.Login(mobileNumber, code)
viewModel.onAction(MyLoginIntent.ResendCode(mobileNumber)

Currently Uniflow is taking care of manipulating and representing state in an exhaustive self documenting way. It is taking care of the flow of state but not really taking care of the flow of intents. What do you think of making this pattern part of Uniflow in some way.

[StephanSchuster]

While I like the idea of encapsulating related things and keeping APIs minimal, I think this would add slightly more complexity/code and especially prevent different usages of action and actionOn, right?

[MarcinChrapowicz]

Not really you can modify this a little and achieve it

sealed class MyLoginIntent {
  data class Login(mobileNumber: String, code: String) : MyLoginIntent()
  data class ResendCode(mobileNumber: String) : MyLoginIntent()
}

class MyLoginViewModel : AndroidDataFlow()
  fun onAction(intent: MyLoginIntent)  {
    when(intent) {
      is MyLoginIntent.Login -> login(intent)
      is MyLoginIntent.ResendCode -> resendCode(intent)
    }  
  }
  
  private suspend fun login(loginIntent: MyLoginIntent.Login) = actionOn<...> { 
     // Manipulate state
  }

  private suspend fun resendCode(resendCodeIntent: MyLoginIntent.ResendCode) = action {  
     // Manipulate state
  }
}

// In our view
viewModel.onAction(MyLoginIntent.Login(mobileNumber, code)
viewModel.onAction(MyLoginIntent.ResendCode(mobileNumber)