documentation/IS4C/developer/api/notifier.html from CORE-POS/IS4C

documentation/IS4C/developer/api/notifier.html
Summary

Maintainability

Test Coverage

Issues
<html>
<head>
    <title>Notifier</title>
</head>
<body>
<div style="text-align:center;">
<h1>Notifier</h1>
<!--
17Jan14 AT Doc first written
-->
<br />as of: January 17, 2014
</div>
<p>
Notifer modules are displayed on the right side of the screen
below the scale weight. They can display information constantly
or conditionally. Notifiers have the following methods:
</p>
<blockquote>
string <b>draw</b>()<br />
void <b>transactionReset</b>()<br />
</blockquote>
<p>
The <b>draw</b> method should return an HTML string containing
the informtion to display. This should almost always include some
block-level HTML tag like a &lt;div;&gt; so that different notifiers
don't run together. Return the empty string if there's nothing to
display currently. The <b>transactionReset</b> method does not
have to do anything. This method is simply called after the end
of each transaction. It is provided as a convenience in case
your Notifier is keeping track of any state that needs to be
reliably reset after a transaction.
</p>
<p>
Developers should be aware that Notifiers will only be
refreshed when a) the whole page reloads or b) a parser triggers
a redraw of that section. Setting a parser's return value for
<i>scale</i> to any non-false value will redraw that section.
This could be refactored if it bothers anyone sufficiently.
</p>
<p>
<b>Example</b>: display the current member's IOU balance
<pre>
class MemBalanceNotifier extends Notifier 
{
    public function draw(){
        global $CORE_LOCAL;

        if ($CORE_LOCAL->get('memberID') == 0 || $CORE_LOCAL->get('memberID') == $CORE_LOCAL->get('defaultNonMem')) {
            return '';
        }

        $db = Database::pDataConnect();

        $query = $db->prepare_statement('SELECT Balance FROM custdata WHERE CardNo=?');
        $result = $db->exec_statement($query, array($CORE_LOCAL->get('memberID')));

        // non-valid member number apparently
        if ($db->num_rows($result) == 0) {
            return '';
        }

        $row = $db->fetch_row($result);

        return sprintf('&lt;div style="border:1px solid black;"&gt;Balance $%.2f&lt;/div&gt;',
                        $row['Balance']);

    }
}
</pre>
</p>
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