Example of how to get a unique ID per type

typeid.nim

import tables

# ---

type ID = int

var nextTypeID {.compileTime.}: ID

proc typeID(T:typedesc): ID =
  const id = nextTypeID
  static:
    inc nextTypeID
  return id

# ---

type Event = proc(): string

var registeredEvents = newTable[ID,Event]()

proc register(T:typedesc, event:Event) =
  registeredEvents[typeID(T)] = event

# ---

type
  Foo = object
  Bar = object

proc aaa: string = "AAA"
proc bbb: string = "BBB"

Foo.register(aaa)
Bar.register(bbb)

for id, event in registeredEvents:
  echo id, ": ", event()

# PRINTS:
# 1: BBB
# 0: AAA