How do you deserialize json into the correct virtual class?

Question

Let's say I have a virtual class and two classes that extend it and I am getting a JSON response that could be either one of those classes. Is there a way to deserialize the JSON into the appropriate class without examining it manually?

Here are my classes:

public with sharing virtual class BaseClass
{
public Integer id;
}

public with sharing class foo extends BaseClass
{
public String foo;
}

public with sharing class bar extends BaseClass
{
public Integer bar;
}

I want to be able to do something like

Json.deserialize(jsonstring,Class.BaseClass.Descendants)

Answer 1

If your JSON always has an id, but also has either a foo or a bar, I think the corresponding Apex would be

public class Thing {
    public Integer id;
    public String foo;
    public Integer bar;
}

You would deserialize into a Thing, then test whether foo or bar was null. There's no way to persuade the parser to pick the correct subclass.

Answer 2

I don't think it is possible.

JSON is a data only object, and has no knowledge of your classes.

You would need to embed the name of your class and check that when de-serializing.