Swift enum nested class VS Kotlin sealed class. Cant understand

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I have code in Swift.

enum QuestionnaireViewMode {
    
    case add(input: Add)
    case edit(input: Edit)
    
    enum Add {
        
        case building(input: BuildingInput)
        case car(input: CarInput)
        case park
        
        struct BuildingInput {
            let address: String
            let placeName: String
        }
        
        struct CarInput {
            let name: String
        }
    }
    
    enum Edit {
        case profile(input: ProfileInput)
        
        struct ProfileInput {
            let name: String
        }
    }
}

This is enum class which very easy to use, for example i can create different type of object just like this: .add(input: .car(input: .init(name: "bmw"))). But for me not clear enum classes in kotlin, i found some similar - sealed class and i tryed converted to:

sealed class QuestionnaireViewMode {
    sealed class add(input: Add)
    sealed class edit(input: Edit)

    sealed class Add {
        sealed class building(input: BuildingInput)
        sealed class car(input: CarInput)
        sealed class park

        data class BuildingInput(val address: String, val placeName: String)
        data class CarInput(val name: String)
    }

    sealed class Edit {
        sealed class profile(input: ProfileInput)
        data class ProfileInput(val name: String)
    }
}

is this correct?

kotlin enums
1 Answers

Your sealed classes need to extend their parent. And you are using sealed class instead of fun for your builder functions, which doesn’t make sense. But since these are classes you don’t need that because you can call the constructors directly. Also, since you have no commonly shared state, these can be sealed interfaces instead of sealed classes, which is a little simpler because you don’t have to worry about constructors.

Here is how I would design it:

sealed interface QuestionnaireViewMode {
    sealed interface Add: QuestionaireViewMode {
        data class BuildingInput(val address: String, val placeName: String): Add
        data class CarInput(val name: String): Add
    }

    sealed interface Edit: QuestionaireViewMode {
        data class ProfileInput(val name: String): Edit
    }
}

Usage:

val myInput: QuestionaireViewMode =
    QuestionaireViewMode.Add.CarInput(“bmw”)
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