This print for content only-size & color not accurate 7" X 9-1/4" / casebound / malloy

// The callback interface.

public interface IEngineNotification

{

C H A P T E R   9  

■

W O R K I N G   W I T H   I N T E R FA C E S

304

8849CH09.qxd  10/1/07  10:41 AM  Page 304

---

void AboutToBlow(string msg);

void Exploded(string msg);

}

Callback interfaces are often not implemented by the object directly interested in receiving the

events, but rather by a helper object called a 

sink object. The sender of the events (the Car type in

this case) will make calls on the sink under the appropriate circumstances. Assume the sink class is

called CarEventSink. When this object is notified of the various incoming events, it will simply print

out the incoming messages to the console. Furthermore, our sink will also maintain a string mem-

ber variable that represents its friendly name (you’ll see how this can be useful as you move through

the example):