Page Comparison

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• Behavior:  Evaluates a value against a regular expression and returns true if the value matches that regular expression.

• Return: true or false

• Arguments:  There are two arguments, the value to be validated and the regular expression as a string. 

• Syntax: regex(value, regular_expression)

• Example:  This is useful when doing complex validation against some value.  For example, to validate that a string contains only numbers, you can use regex(/data/my_question, "^[0-9]+$").   You can test and develop other regular expressions using http://www.regexr.com/.  Also see the Advanced Validation Conditions page.

uuid()

• Behavior:  Calculates a random hexadecimal (0-9, a-f) identifier of 32 characters long.  There are 16^32 = 3.4*10^38 possibilities for this kind of identifier.  The statistical chance that these values are not unique is extremely low, so we call it a unique identifier.  https://en.wikipedia.org/wiki/Universally_unique_identifier

• Return: The unique id.  

• Arguments:  none!

• Syntax: uuid().  Omitting the argument results in a 32 digit unique identifier.

• Examples: uuid() could return 24235c71-09bf-40e8-87d2-00767efd7a14 or 4498b8a9-0af4-4413-994a-ad44e166f073

uuid(argument)

• Behavior:  Calculates a random alphanumeric (0-9, A-Z) identifier of a particular length.  The longer the length, this more likely it is that this random number is unique across the project.  If the argument is 3, then there are 36^3 = 4.7*10^4 possibilities.  This is a large number of possibilities, but not large enough to ensure that there is not a duplicate.  If the argument is 32, there will be 36^32 = 6.3*10^49 possibilities, which is statistically very unlikely to produce a duplicate.  Note that uuid() with an argument is not a traditionally-defined UUID as described here; https://en.wikipedia.org/wiki/Universally_unique_identifier.

• Return: The random id.  

• Arguments:  The length of the random id

• Syntax: uuid(length).

• Examples: uuid(4) could return WZV4 or 5J43.  uuid(32) could return 4KV5JRAUM48YS9SP2SWX2G94UEAJBHXQ or N9HTXSZPJI0H8GQS2SBW88V881CJEN1I.

coalesce

• Behavior:  Useful for choosing which of two values to return.  Will return the non-null/empty value.  If both are not null, will return the first argument.  

• Return: One of the values

• Arguments:  The two values to be coalesced

• Syntax: coalesce(value_1, value_2).  

• Example:  This is useful if you want to use a default value when referring to a question which may or may not have been answered.  Ex. coalesce(/data/my_question, "my default value"). 

• Note: Since CommCare version 2.31, coalesce accepts more than 2 arguments, returning the first non-null argument.

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• Behavior: Takes a json string and a string property name and returns the value of that property from the json string.

• Return: A string value for the property name passed in 

• Arguments: A string (stringified json object), a string property name

• Syntax: json-property(json_string, property_name)

• Example: json-property('{"full":"New Canada St., 3855 Brienz, Switzerland","geopoint":"46.748107 8.0473685","zipcode":"3855","postcode":"3855","city":"Brienz","region":"Bern","state_long":"Bern","state_short":"CH-BE","country":"Switzerland","country_short":"ch","street":"New Canada St."}', 'city') -> "Brienz"

• Since: This function is available in CommCare 2.51 and later.

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• Behavior: 2 strings, each of which should be a space-separated string representing a list of strings, and an optional boolean value indicating the desired sort direction, and returns the result of sorting the 1st list by the 2nd list.

• Return: A string representing a sorted, space-separated list

• Arguments: 2 strings representing space-separated lists, and an optional boolean argument indicating direction (true() is ascending, false() is descending, default is ascending)

• Syntax: sort-by("a b c d", "3 2 4 1", true())

• Examples: 
  

  • sort-by("apple banana chip dog egg flea", "4 2 1 5 3 2") --> "chip banana flea egg apple dog" 

  • sort-by("apple banana chip dog egg flea", "4 2 1 5 3 2", false()) --> "dog apple egg flea banana chip" 

• Since: This function is available on CommCare 2.38 and later

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