#
#
# Nimrod's Runtime Library
# (c) Copyright 2011 Alex Mitchell
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## :Author: Alex Mitchell
##
## This module implements an event system that is not dependant on external
## graphical toolkits. It was originally called ``NimEE`` because
## it was inspired by Python's PyEE module. There are two ways you can use
## events: one is a python-inspired way; the other is more of a C-style way.
##
## .. code-block:: Nimrod
## var ee = initEventEmitter()
## var genericargs: TEventArgs
## proc handleevent(e: TEventArgs) =
## echo("Handled!")
##
## # Python way
## ee.on("EventName", handleevent)
## ee.emit("EventName", genericargs)
##
## # C/Java way
## # Declare a type
## type
## TSomeObject = object of TObject
## SomeEvent: TEventHandler
## var myobj: TSomeObject
## myobj.SomeEvent = initEventHandler("SomeEvent")
## myobj.SomeEvent.addHandler(handleevent)
## ee.emit(myobj.SomeEvent, genericargs)
type
TEventArgs* = object of TObject ## Base object for event arguments that are passed to callback functions.
TEventHandler* = tuple[name: string, handlers: seq[proc(e:TEventArgs) {.closure.}]] ## An eventhandler for an event.
type
TEventEmitter* = object {.pure, final.} ## An object that fires events and holds event handlers for an object.
s: seq[TEventHandler]
EInvalidEvent* = object of EInvalidValue
proc initEventHandler*(name: string): TEventHandler =
## Initializes an EventHandler with the specified name and returns it.
result.handlers = @[]
result.name = name
proc addHandler*(handler: var TEventHandler, func: proc(e: TEventArgs) {.closure.}) =
## Adds the callback to the specified event handler.
handler.handlers.add(func)
proc removeHandler*(handler: var TEventHandler, func: proc(e: TEventArgs) {.closure.}) =
## Removes the callback from the specified event handler.
for i in countup(0, len(handler.handlers) -1):
if func == handler.handlers[i]:
handler.handlers.del(i)
break
proc containsHandler*(handler: var TEventHandler, func: proc(e: TEventArgs) {.closure.}): bool =
## Checks if a callback is registered to this event handler.
return handler.handlers.contains(func)
proc clearHandlers*(handler: var TEventHandler) =
## Clears all of the callbacks from the event handler.
setLen(handler.handlers, 0)
proc getEventhandler(emitter: var TEventEmitter, event: string): int =
for k in 0..high(emitter.s):
if emitter.s[k].name == event: return k
return -1
proc on*(emitter: var TEventEmitter, event: string, func: proc(e: TEventArgs) {.closure.}) =
## Assigns a event handler with the specified callback. If the event
## doesn't exist, it will be created.
var i = getEventHandler(emitter, event)
if i < 0:
var eh = initEventHandler(event)
addHandler(eh, func)
emitter.s.add(eh)
else:
addHandler(emitter.s[i], func)
proc emit*(emitter: var TEventEmitter, eventhandler: var TEventHandler,
args: TEventArgs) =
## Fires an event handler with specified event arguments.
for func in items(eventhandler.handlers): func(args)
proc emit*(emitter: var TEventEmitter, event: string, args: TEventArgs) =
## Fires an event handler with specified event arguments.
var i = getEventHandler(emitter, event)
if i >= 0:
emit(emitter, emitter.s[i], args)
else:
raise newException(EInvalidEvent, "invalid event: " & event)
proc initEventEmitter*(): TEventEmitter =
## Creates and returns a new EventEmitter.
result.s = @[]