XIN Rules

HOME > SETUP > DEVELOPER'S INSTRUMENT GUIDE > HOW TO CODE AN INSTRUMENT > XIN RULES

What are XIN Rules?

XIN Rules validate your input and prevent you from moving forward if you forget to fill in a required field. They can be used to enforce dependencies between fields.

i.e. If A1 is selected in question A and if A2 is selected in question B, then give examiner a break and skip question 3 and 4.

For example:

A. Do you smoke? (Options:) A1: Yes A2: No

> B: How often do you smoke? #Skip question B if A2 "No" response was given for question A

How to use XIN Rules

Enable XIN Rules for your instrument

See Sample Instrument Template for code to invoke XIN rules from the setup() and setupForm() functions

Add XIN Rules to form elements

All elements are required if no rule is specified, unless it is part of a group.

$this->XINRegisterRule(
    "field_name1",
    array("field_name2{@}=={@}yes|maybe|sure"),
    "Required." 
);

$this->XINRegisterRule(
    "field_name", // field name on which the rule is applied
    array("field_name{@}=={@}"), // rule
    "Required.", // message
    "group_1" // group [if field is a part of a group]
);

NOTE: When adding XIN rules some elements are implicitly added to a group in NDB_BVL_Instrument.class.inc. In consequence, a group name needs to be specified when registering a rule. A group name is necessary for the following elements:

$this->addHourMinElement();  // Group name: {$fieldName}_group
$this->addTextElement();  // Group name: {$fieldName}_group
$this->addNumericElement();  // Group name:{$fieldName}_group
$this->addDateElement();  // Group name: {$fieldName}_dategroup

Field is never required

$this->XINRegisterRule(
    "field_name",
    array("field_name{@}=={@}NEVER_REQUIRED"),
    "Not required",
    "group1" 
);

Field is required based on value of another field (check for equality)

$this->XINRegisterRule(
    "field_name1",
    array("field_name2{@}=={@}yes"),
    "Required." 
);

Field is required based on value of another field (check for equality with multiple valid values)

$this->XINRegisterRule(
    "field_name1",
    array("field_name2{@}=={@}yes|maybe|sure"),
    "Required." 
);

Multiple rules applied in AND fashion

$this->XINRegisterRule(
    "field_name3",
    array("field_name1{@}=={@}yes", "field_name2{@}=={@}no"), // Use , (comma) to "AND" the rules
    "Required." 
);

Multiple rules applied in OR fashion

$this->XINRegisterRule(
    "field_name3",
    array("field_name1{@}=={@}yes|field_name2{@}=={@}yes"), // Use | (pipe) to "OR" the rules
    "Required.",
    "group1" 
);

Validating multi-selects

Currently, multi-selects do not work well within XINRules. To validate that a multi-select has been filled, an additional validation function is a best practice, to ensure that an informative error message is displayed for the user, if the multi-select fails validation and the form is not saved.

    function _page1() {
        ...
        $this->addSelect(
            "multiselect_ex",
            "Multi-Select Example",
            $options,
            ["multiple"]
        );
        ...
        $this->form->addFormRule(array(&$this,'validateMultiSelects'));
    }

    function validateMultiSelects($values)
    {
        $errors = array();

        if(empty($values['multiselect_ex'])){
            $errors['multiselect_ex'] = "Required.";
        }
        
        return $errors;
    }

For more on validation functions, see (validation function section under construction)