documentation/IS4C/developer/api/tenders.html
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<title>TenderModule</title>
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<h1>TenderModule</h1>
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13Aug13 AT Doc first written
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<br />as of: August 13, 2013
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<p>
Tender modules may be attached to one or more tenders. Tender modules
can impose error conditions, set up session variables, or display
prompts for the cashier. All modules should inherit from TenderModule.
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<p>
TenderModules have the following properties. The base class constructor
will populate these proprties. Be careful if you choose to override that
function.
<blockquote>
string <b>tender_code</b> (corresponds to opdata.tenders.TenderCode)<br />
string <b>name_string</b> (corresponds to opdata.tenders.TenderName)<br />
string <b>change_type</b> (corresponds to opdata.tenders.TenderType)<br />
string <b>change_string</b> (corresponds to opdata.tenders.ChangeMessage)<br />
number <b>min_limit</b> (corresponds to opdata.tenders.MinAmount)<br />
number <b>max_limit</b> (corresponds to opdata.tenders.MaxAmount)<br />
mixed <b>amount</b> the number entered or boolean False if no number was provided.
</blockquote>
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<p>TenderModules have the following methods:
<ul>
<li>mixed <b>ErrorCheck()</b><br />
This checks the transaction and returns an error if there is any reason the
tender cannot be used. It returns an HTML string describing the problem or
boolean True if no error is found. Note that the base class version of
ErrorCheck() is always called. It's not necessary to duplicate those checks
in subclasses.</li>
<li>mixed <b>PreReqCheck()</b><br />
This sets up any necessary session variables and optionally directs the cashier
to another page. Typically redirects are to get a confirmation before continuing
with the tender. It returns a URL string to redirect or boolean True if no
redirect is necessary. Note that the base class version of PreReqCheck()
is always called. It's not necessary to duplicate any of that functionality in
subclasses.</li>
<li>[none] <b>Add()</b><br />
Add a tender record to the transaction. Not usually overridden.</li>
<li>string <b>ChangeType()</b><br />
Returns the tender code that should be used for the change record (if there is one).
The default is simply the object's <i>change_type</i> property.
</li>
<li>boolean <b>AllowDefault()</b><br />
Allow the tender to be used without specifying an amount.
The default is True.</li>
<li>number <b>DefaultTotal()</b><br />
The value to use for an amount if none has been specified.
The default is the session variable <i>runningTotal</i>.</li>
<li>string <b>DefaultPrompt()</b><br />
Sets up session variables then returns a URL for the prompt page.
Override to alter the prompt text, go to a different page, add
additional actions like check endorsing, etc.</li>
<li>string <b>DisabledPrompt()</b><br />
Returns an HTML error message when an amount is required but
none was provided. Override to alter the message.</li>
</ul>
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<p>
I'm not going to sketch out an illustrative example. Something that tried
to use all the methods at once would be really contrived. I suggest looking
at <i>GiftCardTender.php</i> for a nice example of using <b>ErrorCheck()</b>
and <b>PreReqCheck</b>. <i>GiftCertificateTender.php</i> is a fairly
straightforward example of overriding <b>DefaultPrompt()</b>.
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