Can I create a new function using reflection in Go?

Question

I have an idea to use interfaces in Go to define RPC style interfaces. So for a given service, I might create an interface like this:

type MyService interface{
  Login(username, password string) (sessionId int, err error)
  HelloWorld(sessionId int) (hi string, err error)
}

What I would like to do is use reflection to implement that interface, translating method calls into RPC calls, Marshaling the input parameters, and Unmarshaling the results back into the output of the method. I know that if I can get a []interface{} of the input parameters I can use reflection to make the service call. However I don't see any way to use reflection to dynamically create a value that would implement the interface by calling my reflection-using functions. Does anyone know of a way to do this, even using unsafe?

Answer 1

You can not create a type with attached methods via reflection, as to instantiate an object of that type.

You could possibly achieve this with a lot of hackery through the unsafe package. But even then, it'd be a massive pain.

If you elaborated more on the problem you're trying to solve, the community could come up with alternatives ways of solving it.

Edit (23. July 2015): starting with Go 1.5 there's reflect.FuncOf and reflect.MakeFunc, which do exactly what you want.

Answer 2

It appears that the reflect package will gain the ability to create new arbitrarily typed functions in Go 1.1: reflect.MakeFunc.

(the following added in response to @nemo)

Instead of an interface, one could create a struct type:

type MyService struct{
  Login func(username, password string) (sessionId int, err error)
  HelloWorld func(sessionId int) (hi string, err error)
}

autorpc.ImplementService(&MyService, MyServiceURL)
session, err := MyService.Login(username, password)
stringout, err := MyService.HelloWorld(session)