gecko-dev/xpcom/base/nsIInterfaceRequestor.idl

/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 * 
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 * 
 * The Original Code is the Mozilla browser.
 * 
 * The Initial Developer of the Original Code is Netscape
 * Communications, Inc.  Portions created by Netscape are
 * Copyright (C) 1999, Mozilla.  All Rights Reserved.
 * 
 * Contributor(s):
 *   Travis Bogard <travis@netscape.com>
 */

#include "nsISupports.idl"

/**
 * The nsIInterfaceRequestor interface defines a generic interface for 
 * requesting objects that a given object might implement.  This is very
 * similar to QueryInterface found in nsISupports.  The main difference being
 * that objects returned from this interface are not required to provide a way
 * back to the object implementing this interface.  The semantics of QI() 
 * dictate that given an interface A that you QI() on to get to interface B,
 * you must be able to QI on B to get back to A.  This interface however 
 * allows you to obtain an interface C from A that may or most likely will not
 * have the ability to get back to A. 
 */

[scriptable, uuid(033A1470-8B2A-11d3-AF88-00A024FFC08C)]
interface nsIInterfaceRequestor : nsISupports
{
	/*
	Asks the object for a listener object supporting a particular interface.
	This method is used to allow the listener to not adhere to the
	QI rules.  By providing a a getInterface call the component can have
	completely different objects for each distinct type of interface.
	*/
	void getInterface(in nsIIDRef uuid, 
                      [iid_is(uuid),retval] out nsQIResult result);
};


%{C++

#ifndef nsCOMPtr_h___
#include "nsCOMPtr.h"
#endif

class NS_EXPORT nsGetInterface : public nsCOMPtr_helper
  {
    public:
      nsGetInterface( nsISupports* aSource, nsresult* error )
          : mSource(aSource),
            mErrorPtr(error)
        {
          // nothing else to do here
        }

      virtual nsresult operator()( const nsIID&, void** ) const;
      virtual ~nsGetInterface() {};

    private:
      nsCOMPtr<nsISupports> mSource;
      nsresult*             mErrorPtr;
  };

inline
const nsGetInterface
do_GetInterface( nsISupports* aSource, nsresult* error = 0 )
  {
    return nsGetInterface(aSource, error);
  }

%}