[Android] Set of Conditions with Koin

create functions that validate animal species

1. create an interface to handle

interface AnimalHandler {

    /***
     * @return true end loop
     * @return false continue loop
     */
    fun validate(legs: Int): Boolean
}

2. create a class to handle return boolean after validating (loop of condition)

class AnimalSpeciesHandler(
    val validator: Set<AnimalHandler>
) : AnimalHandler{

    override fun validate(legs: Int): Boolean {
        return validator.firstOrNull {
                   it.validate(legs)
               } != null
    }
}

3. create classes to verify the type of species. for example bird and dog

class Bird(
    private val source: MySource
) : AnimalHandler {

    override fun validate(legs: Int): Boolean {
        return source.legs == legs
    }
}
class Dog(
    private val source: MySource
) : AnimalHandler {

    override fun validate(legs: Int): Boolean {
        return source.legs == legs
    }
}

4. create the module

val animalModule = module {

   factory {
       setOf(
           get<Bird>(),
           get<Dog>()
       )
   }

   factory<AnimalHandler> { AnimalSpeciesHandler(validator = get())}
   factory { Bird(source = get()) }
   factory { Dog(source = get()) }
}

5. how to use inject AnimalHandler(interface) to viewModel and call the function

val inputLegs = 4
val isAnimal = animalHandler.validate(inputLegs)
if(isAnimal) {
    println("It's an animal)
} else {
    println("It's an animal)
}

6. in advance you can throw an Exception and add action including parameter

class Cat(
    private val source: MySource
) : AnimalHandler {

    override fun validate(legs: Int, isFlexibleBody: Boolean): Boolean {
        return isItCat(legs, isFlexibleBody)
    }
private fun isItCat(legs: Int, isFlexibleBody: Boolean) {
        return if(source.legs == legs && !isFlexibleBody) {
                   println("It's might be Dog")
               } else {
                   throw AlienException("Cat")
               }
    }
}

6.1 create Exception

class AlienException(val species: String) : Exception()

6.2 how to use

try {
    val inputLegs = 4
    val isAnimal = animalHandler.validate(inputLegs, true)
}
catch (e: AlienException) {
    println("It's not ${e.species}, it's an alien.")
}

yes, cats are aliens.