DdeCallbackData class

An instance of DdeCallbackData is passed as a parameter to all DDE event callback methods. It contains data about the current event and has a returnValue attribute (set with returnValue:), which is used to return information back to the VA Smalltalk DDE subsystem.

Table 42. DdeCallbackData instance variables

Instance variable (class)	Description
item (String)	Name of the data item
format (String)	Format for the data (see Formats of data transferred between DDE servers and clients).
data (String or ByteArray)	The actual data
application (String)	The server name for this DDE conversation
topic (String)	The topic name for this DDE conversation
reason (Symbol)	Reason this callback is executing (contained in the Pool Dictionary DdeConstants having the form DdeCR...)
returnValue (Boolean or nil)	Value to be returned from the callback. See Table 47 for descriptions of return values and their meanings.

DdeCallbackData has access methods to obtain the server name, the topic name, a data item (name and possibly its value), and data item format specification. The availability and significance of the information in a DdeCallbackData object are event dependent. For a list of callbacks and return values for the DdeServerManager, see Table 45 and Table 47. For a list of callbacks for the DdeClient, see Table 46.