Programmer Reference : Dynamic data exchange : Callbacks for handling DDE events : Return values
Return values
A method responding to a DdeServerManager callback can return information back to the source of the event through the returnValue attribute of a DdeCallbackData object. This value can be set through the returnValue: message. A return value of nil (the default) causes default processing to be performed by the DdeServerManager. The following table describes the return values for DdeServerManager callbacks.
Table 47. DdeCallbackData return values for handling DdeServerManager Callbacks
Callback
Return value: true
Return value: false
Return value: nil
DdeNcoldlinkCallback
The link has been broken.
The link has not been broken.
If there is a link to the item, then break it.
DdeNwarmlinkCallback
The item and format are supported.
The item and format are not supported.
If the item is in the default database, then create a link to it.
DdeNhotlinkCallback
The item and format are supported.
The item and format is not supported.
If the item is in the default database, then create a link to it.
DdeNpokeCallback
The server accepts the data.
The server rejects the data.
The server rejects the data.
DdeNinitiateCallback
N/A. To connect the DDE client send the message notify:ClientOfSupportFor: to the DdeServerManager parameter of the callback.
N/A. To reject the connect request do not send the message notify:ClientOfSupportFor: to the DdeServerManager parameter of the callback.
If the server name and the topic to which the DDE client is attempting to connect exist in the default database, then a connection is made.
DdeNexecuteCallback
The server can run the command.
The server cannot run the command.
The server cannot run the command.
DdeNrequestCallback
The data has been sent to the client. Send the sendItem:value:format: message to the DdeServer parameter of the callback.
The data has not been sent to the client. The VAST DDE subsystem sends a negative acknowledgment to the client.
If the data is in the default database, then it is sent to the client. Otherwise, a negative acknowledgment is sent to the client.
DdeNterminationCallback
N/A
N/A
N/A
For the DdeClient callbacks DdeNchangeCallback, DdeNdataCallback, and DdeNterminationCallback, the return value is ignored whether the return value is true, false, or nil.
Last modified date: 10/08/2020