3.3.3 Connection Points: handling events

The connection points are part of a standard ActiveX mechanism whose primary objective is to allow the ActiveX object to notify its owner of any kind of events. The connection point works as an ``event sink'', where events and notifications go through.

To establish a connection using LuaCOM, the owner of the ActiveX object must create a table to implement the connection interface, whose description is provided by the ActiveX object (this interface is called a source interface) and then call the API method Connect, passing as arguments the LuaCOM object for the ActiveX object and the implementation table. Doing this, LuaCOM will automatically find the default source interface, create a LuaCOM object implemented by the supplied table and then connect this object to the ActiveX object. Here follows a sample:

-- Creates the COM object
--
calendar = luacom.CreateObject("MSCAL.Calendar")

if calendar == nil then
  os.exit(1)
end

-- Creates implementation table
--
calendar_events = {}

function calendar_events:AfterUpdate()
  print("Calendar updated!")
end

-- Connects object and table
--
res = luacom.Connect(calendar, calendar_events)

if res == nil then
  exit(1)
end

-- This should trigger the AfterUpdate event
--
calendar:NextMonth()

It's also possible to separately create a LuaCOM object implementing the connection point source interface and then connect it to the object using AddConnection.

-- Instances the COM object
--
calendar = luacom.CreateObject("MSCAL.Calendar")

if calendar == nil then
  print("Error instantiating calendar")
  os.exit(1)
end

-- Creates implementation table
--
calendar_events = {}

function calendar_events:AfterUpdate()
  print("Calendar updated!")
end

-- Creates LuaCOM object implemented by calendar_events
--
event_handler = luacom.ImplInterface(calendar_events,
  "MSCAL.Calendar",
   "DCalendarEvents")

if event_handler == nil then
  print("Error implementing DCalendarEvents")
  exit(1)
end

-- Connects both objects
--
luacom.addConnection(calendar, event_handler)

-- This should trigger the AfterUpdate event
--
calendar:NextMonth()

-- This disconnects the connection point established
--
luacom.releaseConnection(calendar)

-- This should NOT trigger the AfterUpdate event
--
calendar:NextMonth()