How to count answers to a question in a repeat group in CommCare

A repeat group is capable of iterating over a space separated list with a Model Iteration query, but like any repeat group auto-expansion, this can only occur over a set of values which is fixed when the form opens.

That means the list can't be determined by user input in the form, unless you follow the pattern where the repeat contains an entry for every possible selection, and uses Display Conditions around an inner group to hide elements which aren't chosen.

With those caveats: You can actually accomplish this quite simply, by providing the path to the space separated list as the Model Iteration query itself. Model iterations actually internally operate over a space separated list that they generate by performing a

join(' ', instance('something')/your/iteration/query)

operation on your input. As such, if you provide a query with only one element, the join will just return your space separated list and proceed as usual!

EDIT: Forgot to mention - if you are going to use this method and reference a question inside the form (rather tthan an instance as in my example) it needs to:

• Be set it using a default value, not a calculation
• Needs to come before the model iteration loop.

If question_1 is irrelevant, but the question exists in the form, references to the question will evaluate to an empty value (ie: '') and should not cause errors.

References to the element's node in XML will return an empty set. IE: count(#form/question_1) will return 0.