<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd" MadCap:lastBlockDepth="2" MadCap:lastHeight="120" MadCap:lastWidth="624" MadCap:disableMasterStylesheet="true" MadCap:tocPath="Advanced Features|Refactoring And Schema Evolution|Refactoring Class Hierarchy" MadCap:InPreviewMode="false" MadCap:RuntimeFileType="Topic" MadCap:TargetType="WebHelp" MadCap:PathToHelpSystem="../../../../" MadCap:HelpSystemFileName="index.xml" MadCap:SearchType="Stem"> <head><title>Inserting Class Into A Hierarchy</title> <script type="text/javascript">/* <![CDATA[ */ window.onload = function(){ var pathToFlash = $('html').attr('MadCap:PathToHelpSystem') + 'Content/Resources/Code/ZeroClipboard.swf'; ZeroClipboard.setMoviePath(pathToFlash); function bindToClipBord(element,content){ var clip = new ZeroClipboard.Client(); clip.setText(content); clip.glue(element); }; if(location.protocol==='file:'){ $('.copylink-marker').remove(); } else{ $('.copylink-marker').each(function(){ var text = $(this).parent().parent().children('.prettyprint').html(); $(this).hover(function(){ bindToClipBord(this,text); }, function(){}); }); } prettyPrint(); }; /* ]]> */</script> <link href="../../../SkinSupport/MadCap.css" rel="stylesheet" /> <link href="../../../Resources/Stylesheets/OnlineStyle.css" rel="stylesheet" /> <script src="../../../Resources/Code/prettify.js"> </script> <script src="../../../Resources/Code/lang-vb.js"> </script> <script src="../../../Resources/Code/jquery.min.js"> </script> <script src="../../../Resources/Code/ZeroClipboard.js"> </script> <script src="../../../SkinSupport/MadCapAll.js" type="text/javascript"> </script> </head> <body> <p class="MCWebHelpFramesetLink" style="display: none;"><a href="../../../../index_CSH.html#advanced_topics/refactoring_and_schema_evolution/refactoring_class_hierarchy/inserting_class_into_a_hierarchy.htm" style="">Open topic with navigation</a> </p> <div class="MCBreadcrumbsBox"><span class="MCBreadcrumbsPrefix">You are here: </span><a class="MCBreadcrumbsLink" href="../../../advanced_topics.htm">Advanced Features</a><span class="MCBreadcrumbsDivider"> > </span><a class="MCBreadcrumbsLink" href="../../refactoring_and_schema_evolution.htm">Refactoring And Schema Evolution</a><span class="MCBreadcrumbsDivider"> > </span><a class="MCBreadcrumbsLink" href="../refactoring_class_hierarchy.htm">Refactoring Class Hierarchy</a><span class="MCBreadcrumbsDivider"> > </span><span class="MCBreadcrumbs">Inserting Class Into a Hierarchy</span> </div> <p> <script type="text/javascript">/*<![CDATA[*/document.write('<a href="' + location.href +'">'); document.write("Direct Link"); document.write('</a>');/*]]>*/</script> </p> <p> </p> <h1><a name="kanchor95"></a>Inserting Class Into A Hierarchy</h1> <p>In this example we have a Human-class witch inherits from the Mammal class. Now we want to introduce a new Primate class and let the Human class inherit from it. </p> <p> <img src="../add-new-type-to-hierachy.png" /> </p> <p>Unfortunately db4o doesn't support this kind of refactoring. We need to use a work-around. Basically we create a copy of the Human-class with the new Inheritance-hierarchy and the copy the existing data over.</p> <h2>Step by Step</h2> <ol> <li value="1">Create the new Primate-class</li> <li value="2">Create a copy of the Human-class, for example HumanNew!</li> <li value="3">Change the HumanNew class to inherit from the new Primate-class instead of the Mammal-class.</li> <li value="4">After that, load all existing Human-instances, copy the values over to HumanNew-instances. Store the HumanNew-instance and delete the old Human-instances</li> </ol> <p>Now the objects have the new inheritance hierarchy. You can delete the old Human-class.</p> <div class="codesnippet" MadCap:conditions="Primary.c#"> <pre class="prettyprint" xml:space="preserve">IList<Human> allMammals = container.Query<Human>(); foreach (Human oldHuman in allMammals) { HumanNew newHuman = new HumanNew(""); newHuman.BodyTemperature = oldHuman.BodyTemperature; newHuman.IQ = oldHuman.IQ; newHuman.Name = oldHuman.Name; container.Store(newHuman); container.Delete(oldHuman); }</pre> <div class="codesnippet-meta">AddClassToHierarchy.cs: copy the data from the old type to the new one <div class="codedownload"><a href="../../../CodeExamples/strategies/refactoring/extendhierarchy/Example-refactoring-extendhierarchy-csharp.zip" class="codedownload" MadCap:conditions="Primary.Online">Download Code</a></div><div class="codedownload copylink-marker" MadCap:conditions="Primary.Online"><a href="#copy">Copy Code</a></div></div> </div> <div class="codesnippet" MadCap:conditions="Primary.VB.NET"> <pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim allMammals As IList(Of Human) = container.Query(Of Human)() For Each oldHuman As Human In allMammals Dim newHuman As New HumanNew("") newHuman.BodyTemperature = oldHuman.BodyTemperature newHuman.IQ = oldHuman.IQ newHuman.Name = oldHuman.Name container.Store(newHuman) container.Delete(oldHuman) Next</pre> <div class="codesnippet-meta">AddClassToHierarchy.vb: copy the data from the old type to the new one <div class="codedownload"><a href="../../../CodeExamples/strategies/refactoring/extendhierarchy/Example-refactoring-extendhierarchy-vb.zip" class="codedownload" MadCap:conditions="Primary.Online">Download Code</a></div><div class="codedownload copylink-marker" MadCap:conditions="Primary.Online"><a href="#copy">Copy Code</a></div></div> </div> <p>Note that this example doesn't change existing references from the old instances to the new ones. You need to do this manually as well.</p> <script type="text/javascript" src="../../../SkinSupport/MadCapBodyEnd.js"> </script> </body> </html>