How do I cast a JSON Object to a TypeScript class?

You can't simple cast a plain-old-JavaScript result from an Ajax request into a prototypical JavaScript/TypeScript class instance. There are a number of techniques for doing it, and generally involve copying data. Unless you create an instance of the class, it won't have any methods or properties. It will remain a simple JavaScript object.

While if you only were dealing with data, you could just do a cast to an interface (as it's purely a compile time structure), this would require that you use a TypeScript class which uses the data instance and performs operations with that data.

Some examples of copying the data:

1. Copying AJAX JSON object into existing Object
2. Parse JSON String into a Particular Object Prototype in JavaScript

In essence, you'd just :

var d = new MyRichObject();
d.copyInto(jsonResult);

I had the same issue and I have found a library that does the job : https://github.com/pleerock/class-transformer.

It works like this :

let jsonObject = response.json() as Object;
let fooInstance = plainToClass(Models.Foo, jsonObject);
return fooInstance;

It supports nested children but you have to decorate your class's member.