Grails: Radio button doesn't populate command obj when not selected - forms

Question

When I submit my form, if I do not select a value for my radio box then nothing is sent over to my command object for validation. I don't have issues with textFields or other input types.
class ApplicationCommand implements Validateable {
Map<String,String[]> questions = new LinkedHashMap<String,String[]>();
static constraints = {
questions validator: {val, obj, errors ->
for(String key : val.keySet()) {
errors.rejectValue("questions[${key}]",'required');
}
}
}
}
<g:radioGroup name="cmd.questions[1]" values="['Yes']" labels="['Yes']">
${it.radio}${it.label}
</g:radioGroup>
<g:textField name="cmd.questions[2]" />
With the above example, If i leave both fields empty and I submit I get the following
qusetions = [2: String[0]]
What I expect to see is
questions = [1: String[0], 2: String[0]]
Due to this issue, in my questions validator since key=1 is not populated I cannot validate it. The questions are dynamic all pulled from a DB so I cant hard-code anything in the validator such as if !questions.contains(1). Whatever data is populated into questions upon submission is what I have to assume the data is.
I have found 2 work-arounds, neither of which I like
1) Only for radio buttons, add a hidden field that will force a value to be populated if a radio is not selected. Horribly ugly
<g:hiddenField name="cmd.questions[1]" value="-" />
2) In my validator, I query the DB for all my questions and manually check for the existence of each one in the questions map. I want to avoid DB queries in my validators.
So while my 2 work-around options do work, I don't feel like I should have to resort to them.

Answer 1

I don't think this is a limitation of command objects or Grails; I think it's a limitation of HTML. I see the same question popping up in PHP.
The essential problem is that your command object doesn't know how many questions there are, but is responsible for making sure they are all there. I can think of a couple of (additional) ways to deal with this limitation:
The quick and easy way would be to put a single hidden input with the number of questions into your form. Also ugly, and open to alteration by the end-user.
The other option is to promote questions into a Domain so that the number of questions is known ahead of time, and is made available to your command object via a field or method. Then your command object can ask your questions, "How many are there supposed to be? Okay, did I get that many from the view?" This is similar to your #2 but without having to retrieve an entire collection and iterate it. This also opens up a path to perform further validation on each question (e.g., don't allow text into a numbers-only answer).
This does require hitting the DB, but it's the only way I can think of to validate the number of questions without relying on input from the view. The nice thing is that you can make it a very shallow hit, and hitting the DB can be very quick if you do it properly.