<html>
<head>
<META http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Object Types In TA</title>
<link rel="stylesheet" type="text/css" href="../../../../style.css">
</head>
<body>
<div class="CommonContent">
<div class="CommonContentArea">
<h1>Object Types In TA</h1>
<p>When working in TA enabled environment you must remember that db4o treats Activatable (TA Aware) and non Activatable (other) types differently. </p>
<p>In general we can distinguish the following types:</p>
<ul>
<li>Value types with no identity (char, boolean, integer etc). These types are handled internally by db4o engine and behave the same in TA enabled and disabled modes.</li>
<li>Activatable types, as it is clear from the name, implement Activatable interface and are responsible for their own activation.</li>
<li>Non Activatable type - all the other types, including user types or third-party classes.</li>
</ul>
<p>As it was mentioned <a href="ta_implementation.html" class="wikiLink">before</a> in TA enabled mode non-Activatable types are fully activated whereas Activatable types have 0 activation depth and are getting activated as requested.<br></p>
<p>Let's look at an example model below, which includes Activatable and non-Activatable classes:</p>
<p><img src="Object_Types_In_TA/TA.Gif"/></p>
<p>Querying and traversing in TA enabled mode:</p>
<span name="cs_wiki_filter" csw_filters="cs">
<p>c#: </p>
<p><code>Customer c =
container.Get(typeof(Customer)).Next();</code></p>
</span>
<span name="cs_wiki_filter" csw_filters="vb">
<p>VB: </p>
<p><code>Dim c as Customer =
container.Get(GetType(Customer)).Next();</code></p>
</span>
<p>
At this point the following paths should be already activated (Customer is not Activatable):</p>
<p><code>c.name</code><br>
<code>c.addresses</code><br>
<code>c.addresses[N].firstLine</code><br>
<code>c.addresses[N].country</code> - available but not activated (Activatable type).</p>
<p>Country.getState would cause the Country object to be activated</p>
<span name="cs_wiki_filter" csw_filters="cs">
<p>c#: </p>
<p><code>State state = c.Address[0].Country.GetState(someZipCode);</code></p>
</span>
<span name="cs_wiki_filter" csw_filters="vb">
<p>VB:</p>
<p><code>Dim state As State = c.Address(0).Country.GetState(someZipCode);</code></p>
</span><p>
At this point the following paths become activated<br>
<code>c.addresses[0].country.states</code><br>
<code>c.addresses[0].country.states[N].name</code><br>
<code>c.addresses[0].country.states[N].city</code><br>
<code>c.addresses[0].country.states[N].cities[N]</code>- available but not
activated (Activatable type)</p>
<br>
The following general rules apply:<br>
<ol>
<li>Arrays of Arrays of non Activatable types: non Activatable behavior</li>
<li>Arrays of Arrays of Activatable types: non Activatable behavior except for leaves</li>
<li>JDK collections: non Activatable behavior</li>
<li>Value types with references to non Activatable reference types and to Activatable
reference types: the non Activatable path should be activated fully; Activatable
path stops activation.</li>
</ol>
</div>
</div>
<div id="footer">
This revision (7) was last Modified 2007-12-03T18:08:01 by Tetyana.
</div>
</body>
</html>
