Using velocity for calculations

In the CrossmarX Application Engine velocity can also be used to perform calculations. Velocity calculations are often used in cases where data is required from related classes or when CrossmarX Expressions become too verbose.

Context variables

In velocity calculations, the context already contains some variables.

Variable	Type	Java object	Description
record	input	Record	The record containing all fields of an object.
session	input	Session	Session is the object where all information about a single user session is stored. Every web user has its own Session object
return	output		The variable for setting the value of the calculated field. You have to assign the result of the calculation to this variable. It is read by the component managing calculated fields, which sets the field value to the value read from the variable

Some simple examples

In this example the calculated field of the record gets the same value as the value read from another field of the record:

#set($return = $record.get("other field name"))

The right hand side in the example above is a straight forward value. It can also be an expression with arithmetic or string operators to calculate a value:

#set($return = "field value is " + $record.get("other field name"))

or:

#set($return = 2 * 3)

You can use conditional expressions to get the return value. The ''other field name" should be of datatype decimal or whole number:

#if ($record.get("other field name") > 1)
    #set($return = "many")
#else
    #set($return = "one or less")
#end

You can use loops to add values. Set $return to 0 so the calculation can be made and "field name" should have a numeric datatype

#set($return = 0)
#foreach($rec in $table)
    #set($return = $return + $rec.get("field name"))
#end

Getting a foreign record

An example which uses not only the record itself but a related record. This is where velocity gets really useful.

#set($foreignrecord = $record.getForeignRecord("foreign class name"))
#if($foreignrecord)
    #set($return = $foreignrecord.get("foreign record field name"))
#end

Getting a connected table

An example which uses not only the record itself but a connected table."a field" should have a numeric datatype

#set($return = 0)
#set($connectedTable = $record.getConnectedTable("connected table name"))
#foreach($otherRecord in $connectedTable)
    #set($return = $return + $otherRecord.get("a field"))
#end

An example which uses not only the record itself but a connected table."a field" should have a numeric datatype

This is the same as the previous example but now "a field" is of datatype Money. The use the field in a calculation it has to be converted to cents

#set($return = 0)
#set($connectedTable = $record.getConnectedTable("connected table name"))
#foreach($otherRecord in $connectedTable)
     #set($return = $return + $otherRecord.get("a field").getCents())
#end

Other features - setting the value of another field

A calculated field is a 'read-only' field, since its value is set by the calculation. Besides setting the value of its own field, a calculated field can set the value of another field. Call getEditableRecord() and then set the value

#set($return = some value)
#set($record = $record.getEditableRecord())
$record.put("first name", $return)

Because a calculated field can set the value of other fields, you can use it as a 'field value manager'. The calculated field itself can be hidden

#if($record.get("field name") = value)
    $record.put("other field name", value)
    $record.put("yet another field name", other value)
#else
    $record.put("other field name", alternative value)
    $record.put("yet another field name", other alternative value)
#end

In this case the return variable does not have to be set, because it is without meaning.