with-query-interface Macro

Summary

Used to simplify reference counting when querying a COM interface pointer.

Package

com

Signature

with-query-interface disp interface-ptr {form}* => value*

disp ::= (punknown interface-name &key errorp dispatch)

Arguments

Values

Description

The macro with-query-interface calls query-interface to find an interface pointer for interface-name from the existing COM interface pointer interface-ptr. It evaluates each form with the variable punknown bound to the queried pointer and the pointer is released when control leaves the body (whether directly or due to a non-local exit).

If errorp is true, then punknown is bound to nil if the interface pointer cannot be found, otherwise an error of type com-error is signaled.

If dispatch is non-nil, then a local macro named by dispatch is created as if by with-com-interface to invoke COM interface methods on punknown.

Examples

This example invokes the methods on an i-bar interface pointer queried from an existing interface pointer.

(with-query-interface (p-bar i-bar
                       :dispatch call-bar)
    p-foo
  (call-bar bar-init)
  (call-bar bar-print))

See also

query-interface
release
with-temp-interface