CODEWITHSUNDEEP
oopkotlin
Jan
Jan

Reputation: 17

Kotlin: Cast instance of class to dynamic type

I have a question regarding casting in Kotlin. I want to cast an object that was generated by parsing JSON. The type to which it should be cast will be determined dynamically. This is causing issues which I explain in the comments in the following piece of code:

// interface for objects that are received as json
interface Bundle

// many data classes implementing the Bundle interface
// e.g.
data class DailyPostBundle(/* ... */) : Bundle
data class CreatePostBundle(/* ... */ : Bundle
// ...

val data = /*json string representing a Bundle*/

// logic:

// does this function have to @Operator annotation?
func.findAnnotation<Operator>()?.let {
    // yes it does. is it the right operator?
    if (it.operatorName == operator) {
        // yes it is
        // find the data bundle class from class path
        val bundleClass = Class.forName("$bundleClassesPackage.${type}Bundle")
        // now create an instance of the class from the json string
        val bundle = Gson().fromJson(data, bundleClass)
        // bundle is correctly parsed, BUT: it is of type <Any!>
        // I want to pass it to the function, 
        // therefore it needs to have a type that is an implementation of Bundle, 
        // e.g. DailyPostBundle
        // I cannot cast it explicitly here, the type to which bundle should be cast should be inferred from bundleClass
        // using the dynamically located class works for parsing JSON, but it does not work for casting

        func.call(bundle)  // doesnt work!

        // what I want to do (pseudo-code):
        func.call(bundle as bundleClass) // doesnt compile!
    }
}

Thank you for any suggestions

Upvotes: 1

Views: 3202

Answers (1)

dewey
dewey

Reputation: 312

You should be able to use cast or safeCast.

func.call(bundleClass.cast(bundle))

(Update) Actually, you get a Java class object, so the correct documentation is here.

Also, to use Kotlin's safeCast, you would need to get an instance of the Kotlin class:

bundleClass.kotlin

Upvotes: 1

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