Casting JSON

I'm doing a REST service. A method has as body parameter a JSON corresponding to a class A.

In my production I have class A so that I retrieve the parameters using a dynamic object, such that:

Set body = ##class(%DynamicObject).%FromJSON(%request.Content)
Set myObjectA = ##class(A).%New()
Set myObjectA.Id = body.Id
Set myObjectA.Name = body.Name
Set myObjectA.Date = body.Date
Set myObjectA.Salary = body.Salary

I would like to know if I can avoid doing the manual mapping, doing a casting, since I am sure that FromJSON will return a class A. Something like this:

Set myObjectA = ##class(A).%FromJSON(%request.Content)

Any suggestions? Thanks.