COM Interfaces

The standard COM interfaces that twinBASIC code implements or calls, described with what each method must do and what twinBASIC adds or requires.

A twinBASIC class implements a COM interface with Implements, and calls one through a variable of the interface’s type. Each page gives the interface’s declaration as a twinBASIC project writes it, the contract of each method — what a caller may pass and what the method must return — and the behaviour of the language features that use the interface.

Interfaces

• IUnknown – the base of every interface: asks an object for another interface, and counts its references; what Set, Is and TypeOf use
• IDispatch – finds a member by name and calls it; what an Object variable and CallByName use
• IEnumVARIANT – enumerates a sequence of Variant values; what For Each uses to go through an object
• IErrorInfo and ISupportErrorInfo – describe the error a method failed with; how Err is filled after a failed call
• IConnectionPoint and IConnectionPointContainer – connect an event sink to an object; what WithEvents uses