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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-F32E2F00-B68F-59B2-AABA-181E16354C86" xml:lang="en"><title>The
+object provider (MOP) mechanism</title><prolog><metadata><keywords/></metadata></prolog><conbody>
+<section id="GUID-07E61ABD-C57F-4E11-A32B-85DF6FAC4D61"><title>Purpose</title><p>The object provider mechanism
+exists to enable control types to be established at run time. It's a form
+of Run Time Type Identification (RTTI). More specifically it allows a caller
+to find a control in the run-time hierarchy that implements a particular interface,
+or mixin. From the caller's point of view it's pretty simple: all that's required
+is to ask a control, any control, to get an object that supports the specified
+interface, cast the pointer returned to the correct interface and then call
+the desired function. </p></section>
+<section id="GUID-96964B1B-297B-4196-961F-B574ACBF1811"><title>History</title><p>The Object Provider interface pre-dates
+the parent pointer in <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita"><apiname>CCoeControl</apiname></xref>. Instead it uses a <codeph>MopParent</codeph> pointer
+which is normally the parent control but may be the AppUi or even the <codeph>CoeEnv</codeph> object.
+It was designed to meet Series 60 requirements for navigation of the run-time
+hierarchy. Internally it is now implemented by the framework using the parent
+pointer where possible which simplifies the control development process. </p></section>
+<section id="GUID-8A6CBDB0-343E-41F1-AC3A-876FA6968DB4"><title>Description</title><p>Interfaces are only identifiable by
+the Object Provider framework if they have an associated Interface UID. The
+Interface UID must be declared in the class definition. Fortunately the UID
+is invisible to the caller which simply uses the interface (mixin) name. </p><p>A
+class which implements an identifiable mixin, i.e. one with an Interface UID,
+can 'supply' a pointer to itself when the Object Provider framework requests
+it. If a control is not able to supply the mixin requested it passes the request
+on to the next control in the hierarchy. </p><p>The sequence diagram below
+illustrates the Object Provider process for supplying an interface pointer
+from the run-time hierarchy. </p><fig id="GUID-91496FA9-60F6-5DDA-899B-7E54A8A7E4CB">
+<image href="GUID-DF3ECD47-4A5B-5836-B5CA-ACCEE98412D4_d0e46823_href.png" placement="inline"/>
+</fig><p>Object1 wishes to call a function on <codeph>MInterface</codeph>.
+It calls <codeph>MopGetObject()</codeph> on the nearest control in the run-time
+hierarchy. The Object Provider Framework identifies the Uid for <codeph>Minterface</codeph> and
+then passes the request up the hierarchy until an object is found (Object4)
+that implements <codeph>Minterface</codeph>. </p><p>Calling <codeph>MopGetGetObjectNoChaining()</codeph> will
+call <codeph>MopSupplyObject()</codeph> but not <codeph>MopNext()</codeph>.
+It returns Null if the class does not implement the specified mixin. </p></section>
+<section id="GUID-33E336B0-98AD-45B0-80A8-5263D8D6167D"><title>See also</title> <p><xref href="GUID-B84FA223-3DFD-58C5-8CEF-C5AA73AA6290.dita">How
+to write controls</xref>  </p> </section>
+</conbody></concept>
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