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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-18EF9CFA-5080-5F89-89EC-C64897612D6B" xml:lang="en"><title>How |
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13 to clean up non-CBase classes</title><shortdesc/><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <section id="GUID-DDB53FB1-7E70-45C6-93F8-76FBE03CA6FA"><title>Cleanup for a TAny*</title> <p>This example code shows cleanup |
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15 for a <codeph>TAny*</codeph>, in this case a <codeph>TText</codeph>. </p> <codeblock id="GUID-62C1326A-2C9F-5F57-AA1C-EA557D0FF4FE" xml:space="preserve">TText* buffer=(TText*) User::Alloc(100*sizeof(TText)); |
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16 // create a buffer |
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17 CleanupStack::PushL(buffer); |
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18 // push it to the cleanup stack: treated as TAny* |
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19 TPtr8 bufferPtr(buffer,100); // create a pointer to the buffer |
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20 ... |
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21 // use the buffer |
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22 useBufferL(bufferPtr); |
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23 ... |
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24 // destroy the buffer on the cleanup stack |
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25 CleanupStack::PopAndDestroy(); |
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26 </codeblock> </section> |
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27 <section id="GUID-B2DF0D27-9520-4B7D-A8BC-1B4B1A80A714"><title>Cleanup support for an R class</title> <p>This example code |
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28 shows how to provide cleanup stack support for an <codeph>R</codeph> class. |
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29 To do this, a <codeph>TCleanupItem</codeph> object must be constructed with |
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30 a pointer to the object to clean up, and a pointer to a function that provides |
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31 cleanup for that object. The most effective way to do this is to define a <codeph>TCleanupItem</codeph> cast |
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32 operator in the class. </p> <codeblock id="GUID-FEFC12E2-0BE9-5AEF-89AE-E812651D8AD1" xml:space="preserve">// TCleanupItem operator for objects of this class |
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33 RExampleClass::operator TCleanupItem() |
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34 { |
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35 return TCleanupItem(Cleanup,this); |
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36 }</codeblock> <codeblock id="GUID-5D448C6A-C919-5251-9AC1-139A6F3703FC" xml:space="preserve">...</codeblock> <codeblock id="GUID-92812389-ADAF-554B-BF5E-AA515DF4BFB5" xml:space="preserve">// cleanup function for use by cleanup stack |
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37 static void RExampleClass::Cleanup(TAny *aPtr) |
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38 { |
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39 // Invoke the Close member on the RExampleClass at aPtr |
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40 testConsole.Printf(_L("Doing cleanup.\n")); |
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41 (static_cast<RExampleClass*>(aPtr))->Close(); |
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42 } |
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43 |
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44 // Show use |
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45 void DoTheExampleL() |
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46 { |
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47 RExampleClass r; |
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48 r.Open(); |
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49 // Because RExampleClass has an operator TCleanupItem() |
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50 // pushing it is OK |
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51 CleanupStack::PushL(r); |
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52 |
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53 // ...use r |
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54 // possibly some operations that leave |
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55 |
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56 // PopAndDestroy() invokes RExampleClass::Cleanup() |
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57 CleanupStack::PopAndDestroy(); |
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58 } |
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59 </codeblock> <p><b>Notes</b> </p> <ul> |
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60 <li id="GUID-E8C0A2EF-AD7D-55C9-9805-ADA6072C18F0"><p>The operator returns |
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61 a <codeph>TCleanupItem</codeph> object which is constructed from a pointer |
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62 to the static member function which performs the class’s cleanup processing, |
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63 and a pointer to the object to be cleaned up. </p> </li> |
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64 <li id="GUID-83B10F9E-E07F-59BD-A1A4-62795F6EFF19"><p>The static member function |
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65 which provides the class’s cleanup processing must cast the <codeph>TAny*</codeph> pointer |
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66 into a pointer of the class to be cleaned up. This allows the class member |
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67 function to perform the cleanup </p> </li> |
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68 <li id="GUID-61BAAE8E-C8B4-5034-B4D1-3E31F790B54C"><p> <codeph>CleanupStack::PopAndDestroy()</codeph> removes |
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69 the item from the cleanupstack and invokes the cleanup function defined in |
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70 the <codeph>TCleanupItem</codeph> object. </p> </li> |
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71 <li id="GUID-53F43DCE-9260-5A71-9D59-AABD7916AE9E"><p>Remember that the <codeph>TCleanupItem</codeph> does <i>not</i> go |
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72 onto the cleanupstack. the <codeph>TCleanupItem</codeph> is a container for |
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73 the object that goes onto the cleanupstack. In this example, a pointer to |
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74 the <codeph>RExampleClass</codeph> is put on the cleanupstack. </p> </li> |
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75 </ul> </section> |
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76 </conbody></concept> |