Release 10.1A: OpenEdge Getting Started:
Object-oriented Programming

ON statement

Class files can define static visual objects. The standard Progress visual objects expose a well-defined set of events that an application can respond to, by using the ON statement. The ON statement is supported in the main block of a class file. As noted previously, the main block cannot contain executable code. Therefore a class file cannot specify an ON statement within executable conditional logic, nor can it contain a WAIT-FOR statement in the main block. However, the main block can contain ON statements that respond to a specific event that occurs on a static visual object.

The following code demonstrates this capability:

CLASS Disp:     DEFINE BUTTON msg.    /* These data members are PRIVATE by default. */     DEFINE BUTTON done.     DEFINE FRAME f msg done.     ON 'choose':U OF msg  /* Unconditional ON block valid in the main block. */         MESSAGE "click" VIEW-AS ALERT-BOX.     CONSTRUCTOR PUBLIC Disp ( ):         modal_display ( ).     END CONSTRUCTOR.     METHOD PRIVATE VOID modal_display ( ): /* WAIT-FOR is done in a method. */         ENABLE ALL WITH FRAME f.         WAIT-FOR CHOOSE OF done.     END METHOD. END CLASS.