3.3.3 Connection Points: handling events

3.3.3 Connection Points: handling events

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, cookie = luacom.Connect(calendar, calendar_events)
if res == nil then
  exit(1)
end
-- This should trigger the AfterUpdate event
--
calendar:NextMonth()

The cookie returned by Connect identifies this connection, and can later be used to release the Connection. A COM object can have several event sinks connected to it simultaneously.

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
--
cookie = luacom.addConnection(calendar, event_handler)
-- This should trigger the AfterUpdate event
--
calendar:NextMonth()
-- This disconnects the connection point established
--
luacom.releaseConnection(calendar, event_handler, cookie)
-- This should NOT trigger the AfterUpdate event
--
calendar:NextMonth()

Notice that addConnection also returns a cookie. A call to releaseConnection needs both the event sink and the cookie to release the connection. The old (pre-1.3) syntax of releaseConnection (ommiting the event sink and cookie) still works, but will only release the last connection made (but there will not be leaks, all connections are released when the object is garbage-collected).

• • 3.3.3.0.1 Message loop