CODEWITHSUNDEEP
javascriptclasskotlinkotlin-js-interopkotlin-js
iHad 169
iHad 169

Reputation: 1365

How to JavaScript object to Kotlin class?

I want to get a JavaScript object loaded into a Kotlin class. As a safety check, I need to verify that the Kotlin object is actually the class I’ve created because some JavaScript code parts are not my design. I need the JavaScript to return correctly, but I cannot verify the Kotlin class.

e.g.

JavaScript object

<script id="myJS">
function MyClass(id, name){
    var obj = {};
    obj.id = id;
    obj.name = name;

    return obj;
}
var myClass = MyClass(0, "name_0");
</script>

Kotlin class

class MyClass(
            val id: Int,
            val name: String
)

I use this Kotlin code to get JavaScript object on Kotlin.

val myJS: dynamic = document.getElementById("myJS")
val myClass: MyClass = JSON.parse<MyClass>(JSON.stringify(myJS.myClass))//get JavaScript object
println(myClass.id)//success output "0"
println(myClass.name)//success output "name_0"

println(myClass is MyClass)//but check class this output "false"

How can I verify the JavaScript object is the created Kotlin class?

Upvotes: 2

Views: 2666

Answers (4)

Enaium
Enaium

Reputation: 23

Use serialization

@Serializable
data class MyClass(val id: Int, val name: String)

Json.decodeFromString(MyClass.serializer(), JSON.stringify(js("{}")))

Upvotes: 0

tomschrot
tomschrot

Reputation: 259

This might be helpful:

class MyClass(val id: Int, val name: String) {
    constructor(obj: dynamic): this(obj.id, obj.name)

    override fun toString(): String = 
        "${this.id} ${this.name}"
}

fun main() {

    val obj  = js("{}")
    obj.id   = 1
    obj.name = "Mike"

    val myObj = MyClass(obj)
    println(myObj)
    println(myObj is MyClass)
}

Upvotes: 0

kzm
kzm

Reputation: 395

Use JSON.parse from kotlinx.serialization library instead of JSON.parse from Kotlin/JS standard library.

JSON from Kotlin standard library is just a view around JavaScript JSON object . So JSON.parse creates regular JS object without any information about Kotlin type.

Its fine to use it with external classes that can't be type-checked. But your MyClass is a regular class.

Objects constructed from regular Kotlin classes have special metadata which is essential for type checks myClass is MyClass and reflection myClass::class == MyClass::class. And kotlinx.serialization library creates these full-featured Kotlin objects.

Upvotes: 2

tazzledazzle
tazzledazzle

Reputation: 54

Try this check :

myClass::class == MyClass::class

Upvotes: 0

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