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 IBM Smalltalk DDE subsystem.
Table 41. 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 46 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 44 and Table 46. For a list of callbacks for the DdeClient, see Table 45.