Professional IronPython

Interacting with Predefined and Custom Events
 
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# Import the .NET assemblies.
import System 
import System.Windows.Forms
# import the form. 
from frmCreateEvent import *
# import the NewEventClass.
from NewEventClass import *
# Create the event handler.
def HandleMsg(Msg):
System.Windows.Forms.MessageBox.Show(Msg)
# Define the event and add the handler to it.
ThisEvent = MyEvent()
ThisEvent.Add(HandleMsg)
# Define the event handlers.
def btnFireEvent_Click(*args):
# Fire the event.
ThisEvent.Fire(‘Hello World’)
def btnQuit_Click(*args):
# Close the application.
TestForm.Close()
# Define the Windows Form and the elements of this specific instance.
TestForm = frmMain()
TestForm.InitializeComponent()
# Always add event handlers after defining the Windows Form.
TestForm.btnFireEvent.Click += btnFireEvent_Click
TestForm.btnQuit.Click += btnQuit_Click
# Run the application.
System.Windows.Forms.Application.Run(TestForm)
The code begins like many of the other examples in this chapter — it makes the proper additions to 
sys.path
, creates references to .NET assemblies, and then imports them. Make sure you import all 
the classes required to make your event work. In this case, the code imports both 
frmCreateEvent
and 
NewEventClass
.
The next step is to define an event handler for the new event. This event handler takes a simple 
approach. It accepts 
Msg
from 
Fire()
and displays it using a simple message box similar to the one 
shown in Figure 8-6 (the message is slightly different, but the idea is the same).
Now that there’s an event handler, 
HandleMsg()
, to use, it’s time to assign it to the event. The code cre-
ates a new event, 
ThisEvent
, and assigns 
HandleMsg()
as an event handler to it. In many respects, this 
approach is no different from using a delegate in a .NET language such as C# or Visual Basic .NET. 
The techniques are a bit different, but the basic concept is the same.
548592c08.indd 157
2/24/10 12:48:12 PM
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