The Dispatch Interface of a COM Object is another key COM definition. Broadly speaking, a Dispatch Interface is the actual mechanism that is used by a COM-aware application to communicate with the COM Object. In other words, an application communicates with a COM Object through its Dispatch Interface.
A Dispatch Interface can be represented in a similar manner to a User-Defined Type (UDT), but instead of member variables, an Object's Dispatch Interface members comprise a set of Functions and associated data. See INTERFACE/END INTERFACE for more details of the actual syntax of an Interface representation, along with The PowerBASIC COM Browser for a tutorial on examining the interfaces of objects and generating an interface definition file.
A COM Object may offer an unlimited number of Interfaces, but may expose only one Dispatch Interface. Internally, these Interfaces are exposed through the single Dispatch Interface.
A COM Object must support a Dispatch Interface to be used by PowerBASIC (and Visual Basic). PowerBASIC does not currently support the use of Direct Interfaces. Further, a PROGID and a CLSID must be present to uniquely identify each Dispatch Interface exposed by a COM Object.
See Also
Creating an early-bound object variable