linking UI to application layer

Hi,

I consider myself pretty new to oo, so this question might sound stupid.

How do I link the UI to the application/busines/ domain layer?

I mean can I pass messages from the domain layer to the UI or does the UI send messages?

For instance, to update a result in a textfield do I send a message to the UI to update the textfield or

When event is lauched by pressing the button the UI sends a message to get the result from the domain layer?

[480 byte] By [aus_java_studenta] at [2007-10-3 5:53:34]