Visual Programming User Guide : Using external functions : Dynamic Data Exchange : Introduction to DDE : Unidirectional DDE
Unidirectional DDE
Many times you will not want the DDE Client part to send data to the DDE Server part. You can control whether or not DDE exchanges data in a bidirectional manner through the settings page of your VA Smalltalk connections. To demonstrate this, we'll modify the SameWindow visual part we just created so that changes to the Client Text part do not update the Server Text part.
Open the settings of the DDE Client's item_string attribute to Client Text part's object attribute connection, by selecting Open Settings from the connection's pop-up menu.
You will see a window that looks like the following:
Connetion settings
Check Read-only source and then select Reverse, if necessary, to ensure the connection is from DDE Client1 (item_string) to Text2 (#object). Select OK to accept the changes to the settings page.
Your connections now look like the following:
DDE example
Note that the connection you just modified now has a hollow circle attached to the DDE Client part. This indicates that the DDE Client item_string attribute is read-only for this connection. Now changes will only flow from the DDE Client part to the Client Text part and the Server Text part will no longer be updated when the Client Text part changes.
Save your work and test it as follows:
1. Try typing some text in the Server Text part. The same text will appear, keystroke by keystroke, in the Client Text part.
2. Try typing some text in the Client Text part. The Server Text part remains unchanged.
3. Type another character in the Server Text part. The Client Text part will exactly match the Server Text part.
Last modified date: 06/12/2018