In golang, is it possible to get reflect.Type from the type itself, from name as string?

Question

type t1 struct { i int; s string }
var v1 reflect.Type = /* how to set to t1's reflect.Type? */

1. is it possible to get the reflect.Type of t1 without having to instantiate it?

2. is it possible to get the reflect.Type of t1 from having its name "t1" as a string?

Hippocrene

Answer 1

On 1, yes, kinda:

var v1 reflect.Type = reflect.TypeOf((*t1)(nil)).Elem()
fmt.Println(v1)  // prints "main.t1"

No instantiation needed. However, Go doesn't have type literals, which is I think what you're asking for. To get the runtime value of a type, you need to have a value of some sort. If you don't want to or can't create the value at runtime, you can pull it from a typed nil. If you don't like the idea of looking this up every time, you can store this runtime type in a variable.

On 2, no, not really. This would require the Go runtime to maintain a map of all types in the current binary, which has a number of problems. You could create a type registry package, and register all types you may want to retrieve by string, but that's always going to be incomplete, and if you know what type you want, you can always just use TypeOf. The situation is made a bit more complicated by the fact that you can have anonymous types, and the name like "t1" isn't certain to be unique, as another package may have a type of the same name. It is possible for the Go runtime to provide a function that gives a type from a string name, but I doubt that will happen.

Nonferrous

thanks. everything you said makes perfect sense. using nil was nicely sneaky - had not seen that trick before. – Hippocrene

reflect.TypeOf((*t1)(nil)).Elem().Name() gives you just "t1" (i.e. struct name without the package) – Glow

much like pass a (undefined :: Type) as a type parameter instead a value parameter in haskell – Ramsgate