class DDETopic
Topic group Related topics Example
Determines the actions taken when dBASE Plus receives requests from a DDE client.
Syntax
[<oRef> =] new DDETopic(<topic expC>)
<oRef>
A variable or property in which to store a reference to the newly created DDETopic object. This object reference must be returned by the _app object’s onInitiate event handler.
<topic expC>
The name of the topic to which the DDETopic object responds.
Properties
The following tables list the properties, events, and methods of the DDETopic class.
|
Property |
Default |
Description |
|
DDETOPIC |
Identifies the object as an instance of the DDETopic class | |
|
(DDETOPIC) |
Identifies the object as an instance of a custom class. When no custom class exists, defaults to baseClassName | |
|
|
The DDETopic object's topic |
|
Event |
Parameters |
Description |
|
<item expC> |
After an external application creates a hot link | |
|
<cmd expC> |
When a client application sends a command to dBASE Plus | |
|
<item expC> |
When the client requests a value from dBASE Plus | |
|
<item expC>, |
When the client sends a new value for a dBASE Plus item | |
|
<item expC> |
After a client removes a hot link from a particular item |
|
Method |
Parameters |
Description |
|
<item expC> |
Notifies all interested client applications that a dBASE Plus item was changed | |
|
|
Explicitly removes the DDETopic object from memory |
Description
Use a DDETopic object to determine what dBASE Plus does for a client application when dBASE Plus is the server in a DDE link. dBASE Plus may act as a DDE server for one or more topics; client applications must specify the topic they are interested in when they create the DDE link. (A client application may link to more than one topic at a time.)
As a server application, dBASE Plus accepts either a generic command string, or a named item-value pair from a client application. It must respond to requests for a named data item, and notify interested client applications when a item value changes.
You usually create a DDETopic object in an initiation-handler routine, which you assign to the onInitiate event of the _app object. The initiation-handler executes when a client application requests a DDE link with dBASE Plus and no DDETopic object exists in memory for the desired topic. Each newly-created DDETopic object must be returned by the onInitiate event handler; that object is automatically stored internally to respond to client requests on that topic.
When dBASE Plus acts as a DDE server, the topics and item names it maintains internally are not case-sensitive; topic and item names that match existing names (regardless of case) will be changed to those names before being passed to events. When writing event handlers, be aware that the names may vary in case—use UPPER( ) or LOWER( ) to make the names consistent in the program logic.
For information on using dBASE Plus as a client application, see class DDELink.