Event System

gistfile1.nim

import StrUtils

# ---

type Foo =
  ref object
    value: int

type Bar =
  ref object
    value: char

proc update(f:Foo) = echo f.value
proc update(b:Bar) = stdout.write(b.value)

# ---

proc updateItems[T]: var seq[T] {.inline noInit.} =
  var items{.global.}: seq[T] = @[]
  return items

proc updateAll[T] =
  for i in updateItems[T]():
    update(i)

# ---

var updates: seq[proc(){.nimcall.}] = @[]

proc setup =
  # add instances
  updateItems[Foo]().add(Foo(value:256))
  updateItems[Bar]().add(Bar(value:'h'))
  updateItems[Bar]().add(Bar(value:'i'))
  updateItems[Bar]().add(Bar(value:' '))
  
  # add events
  updates.add(updateAll[Foo])
  updates.add(updateAll[Bar])
  
  # print help message
  echo "type 'exit' to quit"
  echo "type 'exec' to execute all updates"
  echo "type 'foo <int>' to add a new Foo"
  echo "type 'bar <char>' to add a new Bar"

proc run =
  while true:
    var line = readline(stdin)
    if line.len >= 4:
      case line[0..3]:
        
        of "foo ":
          updateItems[Foo]().add(Foo(value:parseInt(line[4..line.high])))
        
        of "bar ":
          updateItems[Bar]().add(Bar(value:line[4]))
        
        of "exec":
          for u in updates: u()
          echo ""
        
        of "exit":
          break
        
        else:
          echo "Please entry a valid command"

# ---

when isMainModule:
  setup()
  run()