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NativeScript Core

Creating New Classes

It is one thing to access native Android APIs and another to inherit existing classes and/or create interface implementations and literally every application needs such functionality. Consider the following code snippet:

var myObject = java.lang.Object.extend({
    hashCode: function(){
        return 10;

In this example we extend (or inherit in terms of OOP) java.lang.Object and create a new type, overriding the hashcode method. In Android, the same code would look like:

public class MyObject { // implicit base class is java.lang.Object
    public int hashCode(){
        return 10;
class MyObject { // implicit base class is kotlin.Any
    override fun hashCode(): Int {
        return 10

When a class is inherited in Android, the compiler creates a new class, containing the user-defined logic. But what about NativeScript where the JavaScript code is processed at runtime, meaning this happens after the Compiler step?

Binding (Dynamic Type) Generator

This is one of the major modules within the NativeScript Android Runtime and it is responsible for the generation of new Android Types (Classes). When an extend call is received, the generator takes the provided JavaScript literal, containing the method overrides, and creates a new Java class at runtime. When an overridden method is called upon an instance of such dynamic type, the Runtime will directly call the provided JavaScript method implementation (if any):

var myObjectInstance = new myObject();
var hashCode = myObjectInstance.hashCode(); // will return 10, as specified in the extend function

See Also