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<title>Working with Sequenced Data Objects</title>
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</div><hr /><div id="sdo.sample.sequence" class="section">
<h2 class="title">Working with Sequenced Data Objects</h2>
<p class="para">
Sequenced data objects are SDOs which can track property
ordering across the properties of a data object. They can also
contain unstructured text elements (text element which do not
belong to any of the SDO's properties). Sequenced data objects are
useful for working with XML documents which allow unstructured text (i.e.
mixed=true) or if the elements can be interleaved (
<div class="cdata"><pre><A/><B/><A/></pre></div>). This can occur for example when
the schema defines maxOccurs>1 on a
element which is a complexType with a choice order indicator.
</p>
<p class="para">
The examples below assume an SDO created with the following schema
and instance information, using the XML Data Access Service.
</p>
<p class="para">
The schema below describes the format of a letter. The letter can
optionally contain three properties; date, firstName, and lastName.
The schema states <strong class="command">mixed="true"</strong> which means that
unstructured text can be interspersed between the three properties.
</p>
<p class="para">
<div class="example-contents">
<div class="xmlcode"><pre class="xmlcode"><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:letter="http://letterSchema"
targetNamespace="http://letterSchema">
<xsd:element name="letters" type="letter:FormLetter"/>
<xsd:complexType name="FormLetter" mixed="true">
<xsd:sequence>
<xsd:element name="date" minOccurs="0" type="xsd:string"/>
<xsd:element name="firstName" minOccurs="0" type="xsd:string"/>
<xsd:element name="lastName" minOccurs="0" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:schema></pre>
</div>
</div>
</p>
<p class="para">
The following is an instance letter document. It contains the
three letter properties; date, firstName and lastName, and has
unstructured text elements for the address and letter body.
</p>
<p class="para">
<div class="example-contents">
<div class="xmlcode"><pre class="xmlcode"><letter:letters xmlns:letter="http://letterSchema">
<date>March 1, 2005</date>
Mutual of Omaha
Wild Kingdom, USA
Dear
<firstName>Casy</firstName>
<lastName>Crocodile</lastName>
Please buy more shark repellent.
Your premium is past due.
</letter:letters></pre>
</div>
</div>
</p>
<p class="para">
When loaded, the letter data object will have the sequence and
property indices shown in the table below:
<table class="doctable informaltable">
<thead>
<tr>
<th>Sequence Index</th>
<th>Property Index:Name</th>
<th>Value</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>0</td>
<td>0:date</td>
<td>March 1, 2005</td>
</tr>
<tr>
<td>1</td>
<td>-</td>
<td>Mutual of Omaha</td>
</tr>
<tr>
<td>2</td>
<td>-</td>
<td>Wild Kingdom, USA</td>
</tr>
<tr>
<td>3</td>
<td>-</td>
<td>Dear</td>
</tr>
<tr>
<td>4</td>
<td>1:firstName</td>
<td>Casy</td>
</tr>
<tr>
<td>5</td>
<td>2:lastName</td>
<td>Crocodile</td>
</tr>
<tr>
<td>6</td>
<td>-</td>
<td>Please buy more shark repellent.</td>
</tr>
<tr>
<td>7</td>
<td>-</td>
<td>Your premium is past due.</td>
</tr>
</tbody>
</table>
</p>
<p class="para">
To ensure sequence indices are maintained, sequenced data objects
should be manipulated through the SDO_Sequence interface.
This allows the data object's instance data to be manipulated
in terms of the sequence index as opposed to the property index
(shown in the table above).
The following examples assume the letter instance has been
loaded into a data object referenced by the variable
<strong class="command">$letter</strong>.
<div class="example" id="example-5457">
<p><strong>Example #1 Getting the SDO_Sequence interface</strong></p>
<div class="example-contents"><p>
We obtain a data object's sequence using the
<span class="function"><strong>getSequence()</strong></span>
method. The follow gets the
sequence for the letter data object.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /> $letter_seq </span><span style="color: #007700">= </span><span style="color: #0000BB">$letter</span><span style="color: #007700">-></span><span style="color: #0000BB">getSequence</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
All subsequent examples assume that the
<strong class="command">$letter_seq</strong>
variable has been assigned the sequence for the letter data object.
</p>
<p class="para">
<div class="example" id="example-5458">
<p><strong>Example #2 Get/set sequence values</strong></p>
<div class="example-contents"><p>
We can get and set individual values (including unstructured text)
using the sequence index.
The following sets the firstName to 'Snappy' and gets the last
sequence values (the unstructured text, 'Your premium is past due.').
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /> $letter_seq</span><span style="color: #007700">[</span><span style="color: #0000BB">4</span><span style="color: #007700">] = </span><span style="color: #DD0000">'Snappy'</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$text </span><span style="color: #007700">= </span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">[</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">) - </span><span style="color: #0000BB">1</span><span style="color: #007700">];<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-5459">
<p><strong>Example #3 Sequence iteration</strong></p>
<div class="example-contents"><p>
We can iterate through the individual sequence values using <a href="control-structures.foreach.html" class="link">foreach</a>.
The following runs through the individual values in sequence order.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">foreach (</span><span style="color: #0000BB">$letter</span><span style="color: #007700">-></span><span style="color: #0000BB">getSequence</span><span style="color: #007700">() as </span><span style="color: #0000BB">$value</span><span style="color: #007700">) {<br /> </span><span style="color: #FF8000">// ...<br /></span><span style="color: #007700">}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-5460">
<p><strong>Example #4 Sequence versus Data Object</strong></p>
<div class="example-contents"><p>
Setting values through the data object interface may result in the
value not being part of the sequence. A value set through the data
object will only be accessible through the sequence if the property was
already part of the sequence. The following example sets the
lastName through the data object and gets it through the sequence.
This is fine because lastName already exists in the sequence. If
it had not previously been set, then lastName would be set to
'Smith', but would not be part of the sequence.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /> $letter</span><span style="color: #007700">[</span><span style="color: #0000BB">2</span><span style="color: #007700">] = </span><span style="color: #DD0000">'Smith'</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$last_name </span><span style="color: #007700">= </span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">[</span><span style="color: #0000BB">5</span><span style="color: #007700">];<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-5461">
<p><strong>Example #5 Adding to a sequence</strong></p>
<div class="example-contents"><p>
We can add new values to a sequence using the
<span class="function"><a href="sdo-sequence.insert.html" class="function">SDO_Sequence::insert()</a></span>
method. The following examples assume that the 'firstName' and
'lastName' properties are initially unset.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /> </span><span style="color: #FF8000">// Append a firstName value to the sequence<br /> // value: 'Smith'<br /> // sequence index: NULL (append)<br /> // propertyIdentifier: 1 (firtName property index)<br /> </span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(</span><span style="color: #DD0000">'Smith'</span><span style="color: #007700">, </span><span style="color: #0000BB">NULL</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /><br /> </span><span style="color: #FF8000">// Append a lastName value to the sequence<br /> // value: 'Jones'<br /> // sequence index: NULL (append)<br /> // propertyIdentifier: 'lastName' (lastName property name)<br /> </span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(</span><span style="color: #DD0000">'Jones'</span><span style="color: #007700">, </span><span style="color: #0000BB">NULL</span><span style="color: #007700">, </span><span style="color: #DD0000">'lastName'</span><span style="color: #007700">);<br /><br /> </span><span style="color: #FF8000">// Append unstructured text<br /> // value: 'Cancel Subscription.'<br /> // sequence index: absent (append)<br /> // propertyIdentifier: absent (unstructured text)<br /> </span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(</span><span style="color: #DD0000">'Cancel Subscription.'</span><span style="color: #007700">);<br /><br /> </span><span style="color: #FF8000">// Insert new unstructured text. Subsequent sequence values<br /> // are shifted up. <br /> // value: 'Care of:'<br /> // sequence index: 1 (insert as second element)<br /> // propertyIdentifier: absent (unstructured text)<br /> </span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(</span><span style="color: #DD0000">'Care of:'</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-5462">
<p><strong>Example #6 Removing from a sequence</strong></p>
<div class="example-contents"><p>
We can use the <span class="function"><a href="function.isset.html" class="function">isset()</a></span> and
<span class="function"><a href="function.unset.html" class="function">unset()</a></span> functions to test and remove items
from the sequence (Note: <span class="function"><a href="function.unset.html" class="function">unset()</a></span> currently
leaves the values in the data object, but this behaviour is
likely to change to also remove the data from the data object).
A sequence behaves like a contiguous list; therefore, removing
items from the middle will shift entries at higher indices
down. The following example tests to see if the first sequence
element is set and unsets it if is.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /> </span><span style="color: #007700">if (isset(</span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">])) {<br /> unset(</span><span style="color: #0000BB">$letter_seq</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">]);<br /> }<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
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