ViewModel

Last modified: 06 March 2024

the ViewModel acts as a mediator between the UI layer and the domain layer, which contains the business logic. It focuses solely on managing the presentation logic, handling user interactions, and updating the UI accordingly.

Current code

note

This is under evaluation and incomplete.

ViewModel.kt

class ViewModel(private val mainScreen: MainScreen = MainScreen()) {

    fun getState(): MainState {
        val result = mainScreen fetches platformName
        return result.reduceToState()
    }
}

fun String.reduceToState(): MainState {
    val state = MainState()
    if (isEmpty()) state.error = "Error can't fetch data"
    if (isNotEmpty()) state.success = this
    return state
}

class MainScreen(private val repository: Repository = DataRepository()) {
    infix fun fetches(useCase: Repository.() -> String): String {
        return repository.useCase()
    }
}

data class MainState(
    var success: String = "",
    var error: String = ""
)

ViewModel

class ViewModel(private val mainScreen: MainScreen = MainScreen()) {

}

The ViewModel class encapsulates the logic for managing data and state transitions within the application.

It interacts with the MainScreen to fetch platform-specific data and then processes it to derive the application's current state.

getState

fun getState(): MainState {
    val result = mainScreen fetches platformName
    return result.reduceToState()
}

The getState function within the ViewModel class retrieves the current state of the application.

It delegates the task of fetching platform-specific data to the MainScreen, then processes the result to derive the application state using the reduceToState extension function.

reduceToState

fun String.reduceToState(): MainState {
    val state = MainState()
    if (isEmpty()) state.error = "Error can't fetch data"
    if (isNotEmpty()) state.success = this
    return state
}

The reduceToState extension function operates on a String object, transforming it into a MainState object based on certain conditions.

  • If the string is empty, it sets an error message in the state indicating data retrieval failure.

  • If the string is not empty, it sets the success message in the state with the retrieved data.

MainScreen

class MainScreen(private val repository: Repository = DataRepository()) {
    infix fun fetches(useCase: Repository.() -> String): String {
        return repository.useCase()
    }
}

The MainScreen class serves as an entry point for fetching platform-specific data.

It delegates data retrieval tasks to a Repository implementation and provides a convenient DSL-style function fetches for invoking data retrieval use cases.

MainState

data class MainState(
    var success: String = "",
    var error: String = ""
)

The MainState data class represents the current state of the application.

It contains fields to hold success and error messages, providing a structured way to communicate the outcome of data retrieval operations to other components in the application.