Examples
Say you have a Yes/No Answer field (before 2016.1 called Boolean Input), named yes-no, and if the answer is Yes, you would like to show another field. In the Visibility expression for this other field, you should write:
$yes-no/string() = 'true'
Why not just write
$yes-no? If you do, the expression will always evaluate to true, because Orbeon Forms evaluatesboolean($yes-no): since$yes-nopoints to a node, thebooleanfunction always returns true.Why not write
$yes-no = true()? In this case, since$yes-nocompared to boolean value, it is atomized. The node pointed to by$yes-nois of type boolean, so the atomization process takes the node typed value. When the node contains the stringtrueorfalse, this expression works as expected. However, if it contains an empty string, which up to Orbeon Forms 2017.2 is the default value for that field, then the expression fails. For the purpose of determining whether a field is valid, read-only, or visible, when the expression fails the result will be considered to befalse, so it will work if the expression is used on its own. However, if the expression is used in anorclause ($yes-no = true() or something), if the$yes-no = true()part is evaluated first, the expression as a whole will fail and return false, which is incorrect in case the other part of theorclause is true. Also, in the case of a calculated value, the result will be the empty string, instead offalse.
Scenario: compute the sum of values in multiple repeat iterations. Say you have:
a repeated grid
a decimal field called
priceon each rowan integer field called
quantityon each rowa decimal text output field called
row-totalon each rowa decimal text output field called
totalbelow the grid
You want to compute the row totals and athe general total.
Calculated value expression for row-total:
$price * $quantity
Calculated value expression for total:
sum($row-total[string() castable as xs:decimal], 0.0)
Explanation:
when accessing control values with variables, the "closest" variables are found
this means that the
row-totalcontrol calculation applies to the closestpriceandquantitycontrols, that is, those on the same row, and each row gets its own totalthe
totalcalculation is outside the repeat, and when it refers to$row-total, allrow-totalvalues are returnedsum()is a standard XPath function to compute the sum of a sequence of itemsthe predicate
[string() castable as xs:decimal]excludes values that are blank or not a decimal numbersee this blog post for the use of
string()within the predicatesum()supports a second argument which is the value to return in case no value satisfies the predicate (this makes sure that we return a decimal value, as we are using a literal decimal 0.0)
See also:
Scenario: compute the sum of values in multiple repeat iterations.
Say you have:
a repeat called
my-repeatwith a decimal field called
numberon each row
Calculated value expression:
sum($my-repeat/number[string() castable as xs:decimal])
Explanation:
$my-repeatpoints to the repeat data's enclosing XML elementsthe nested
/numberpath points to thenumberfield within each iteration[string() castable as xs:decimal]excludes values that are blank or not a decimal numbersum()is a standard XPath function to compute the sum of a sequence of items*
Constrain a number between two values
Scenario: Make the current integer number field valid only if its value is between two values, say 12 and 17 included.
Expression:
. >= 12 and . <= 17
Explanation:
.refers to the current value of the control>=orgemeans "greater than or equals to"<=orlemeans "less than or equals to"andis the logical "and" operator
If you want to refer to a specific control by name, you can use:
$my-control >= 12 and $my-control <= 17
Scenario: Make the current field valid only if its length is between two values, say 2 and 140.
Expression:
string-length(.) >= 2 and string-length(.) <= 140
Explanation:
.refers to the current value of the controlThe standard
string-length()function returns the length of its argument>=orgemeans "greater than or equals to"<=orlemeans "less than or equals to"andis the logical "and" operator
If you want to refer to a specific control by name, you can use:
string-length($message) >= 2 and string-length($message) <= 140
[SINCE Orbeon Forms 4.10]
The same can be expressed, for the current control, as:
xxf:min-length(2) and xxf:max-length(140)
Scenario: check that a given value matches a regular expression, for example "only ASCII letters and digits, the dash, and underscore character".
matches(., '^[A-Za-z0-9\-_]+$')
Explanation:
the standard
matches()function applies the regular expression passed as second argument to the first argument, and returns true if it does match
Scenario: check that a given number value is either blank or has exactly 5 digits.
matches(string(.), '\d{5}') or xxf:is-blank(string(.))
Explanation:
the standard
matches()function applies the regular expression passed as second argument to the first argument, and returns true if it does matchthe built-in
xxf:is-blank()function returnstrue()if the value passed is blanksince the data is a number, we use the
string(.)function to convert the value to a string before passing it to functions
Scenario: Make a control read-only if the value of the first-name control is blank:
Expression:
xxf:is-blank($first-name)
Explanation:
$first-namereturns the value of the control with name "first-name"the built-in
xxf:is-blank()function returnstrue()if the value passed is blank
Scenario: As a form author, you can set a static initial value for a control simply by setting that value at design time. For example:
Enter a value in an input field
Select an item in a dropdown list
But not all initial values can be static. For example, you might want a date selection control to contain the current date until the user changes it. In this case, you can use an "Initial Value" expression.
Initial Value expression:
current-date()
Explanation:
current-date()is a standard XPath function returning the current date.
Scenario: compute the sum of two numbers entered by the user in two fields, "quantity1" and "quantity2".
Calculated Value expression:
if ($quantity1 castable as xs:integer and $quantity2 castable as xs:integer)then $quantity1 + $quantity2else ''
Explanation:
if (...) then ... else ...evaluates a condition and then returns one of two alternativesthe condition
quantity1 castable as xs:integerchecks that the value from the field "quantity1" is an integerquantity1 + $quantity2simply adds the two valuesthe value
''represents an empty stringThis can be specified for example on a Text Output control.
NOTE: If the value of a control is calculated, by default it is also marked as read-only. If you want a calculated control to be still editable by the user, set its Read-Only property explicitly to false().
Given this form and a control called name within a repeat:
$name[2]: return the value of the control in the second iterationstring-join($name, ', '): join all values with commascount($name): return the number of values
NOTE: This works when the expression is outside repeat iterations. For expressions within the same repeat, $name returns the closest control.
See also Model bind variables and this StackOverflow question.
See Form Fields.
The Form Runner detail page can have the following modes:
neweditviewpdfemailtest(when you are testing a form within Form Builder)
You can use the fr:mode() XPath function exposed by Form Runner to all XPath expressions.
fr:mode() = 'edit'
A special XPath variable named $fr-mode is exposed by Form Runner to all XPath expressions.
You can test the mode as follows, for example in a Visibility expression:
$fr-mode = 'edit'
It can be useful to access HTTP headers to set default values upon form initialization, for example when single sign-on systems use HTTP headers as a way of communicating information to an application.
XPath expressions have access to a special function, xxf:request-header(), which allows retrieving a header by name. Example of setting the default value of a field using an initial value:
xxf:get-request-header('full-name')
NOTE: With Orbeon Forms 3.8 and 3.9, headers cannot be reliably accessed after the form is initialized, so this function should be used for setting initial values on controls only. See the next scenario for a workaround.
Scenario: field my-attachment must be a PDF file.
Constraint expression:
ends-with(lower-case($my-attachment/@filename), '.pdf')
Explanation:
Form Runner stores information about a file into XML attributes:
@filenameaccesses the file name as sent by the user's browser@mediatypeaccesses the file type as sent by the user's browser@sizeaccesses the file size
$my-attachment/@filenamereturns the file name associated with attachment "my-attachment"The
lower-case()function converts that name to a lower case valueThe
ends-with()function checks whether its first argument ends with the second argument
Similarly, you can test the file type:
$my-attachment/@mediatype = 'application/pdf'
NOTE: Because the file name and file type are sent by the client's browser, they cannot be trusted. This should only be considered a first level of data validation, and further validation based on the content must be performed at a later time if needed. See also issue #1838.
Scenario: We want to set the value of a field from a URL parameter, but only if that parameter exists. If it doesn't, we want to leave the value of the field as it is.
(xxf:get-request-parameter('my-parameter'), .)[1]
Explanation:
If the parameter exists
xxf:get-request-parameter()returns a single stringso you get a sequence containing that string following by the current value of the field
we take the first value of the sequence, so the value of the parameter is used
if the parameter doesn't exist
xxf:get-request-parameter()returns an empty XPath sequenceso you get a sequence containing only the current value of the field
we take the first value of that sequence, so we get the current value of the control
Scenario: For a given set of checkboxes, make sure the number of selected checkboxes is at most 3.
count(xxf:split(.)) le 3
Explanation:
xxf:split(.)tokenizes the space-separated values selected by the checkboxthe number of tokens obtained with
count()corresponds to the number of selected checkboxesthen this makes sure the number of tokens is lower than or equal to 3
Input – In the following XPath expression, the start and end dates are inline, so you'll most likely want to modify it to refer to, say, dates entered by users in a form fields.
Weekends – The expression takes Saturday and Sunday to be part of the weekend.
First day of the week – The expression assumes Monday is the first day of the week. For instance check that on your system
format-date(xs:date('2018-12-10'), '[F1]')returns 1. If not, you'll need to change the expressions for$startWand$endW.Credits – This is a translation to XPath of Java code written by Roland.
for$start in xs:date('2018-12-15'),$end in xs:date('2018-12-26'),$startW in xs:integer(format-date($start, '[F1]')),$endW in xs:integer(format-date($end, '[F1]')),$days in days-from-duration($end - $start),$daysNoWeekends in $days - (floor($days div 7) * 2)returnif ($days mod 7 != 0 and ($startW = 7 or $endW = 7)) then $daysNoWeekends - 1else if ($endW < $startW) then $daysNoWeekends - 2else $daysNoWeekends
Formulas
