The checkboxes have to be added in the form creation stage, so in either hook_form or hook_form_alter. Then in the hook_validate, set a variable on $form_state['storage'] and set $form_state['rebuild'] = TRUE; and check in your hook_form or hook_form_alter for your $form_state['storage'] setting, and if set then add your checkboxes.

I suggest looking at the form_example_wizard in the examples module, as that's basically what you are after, even though it's not a typical multi-step wizard you are after, the logic is still the same. 
Jamie Holly
http://hollyit.net
On 2/11/2015 10:43 AM, Jeff Greenberg wrote:
One thing that is either part of the issue, or a separate issue that impacts this, is that the checkboxes field is added via hook_form_alter. I notice that although the field appears in $form_state[values] it does not appear in $form_state[field], so I'm wondering where $form_state gets the information for the field when rebuilding the form.

On Wed, Feb 11, 2015 at 9:31 AM, Jeff Greenberg <listmail.ayendesigns@gmail.com> wrote:

I have a node form that contains a checkboxes field with options NULL at the time the form is displayed.

During node_validate, if certain criteria is met, an array of options (checkboxes) is created, and the form needs to be redisplayed with the checkboxes as part of it.

I've tried setting #options = the new array in the $form, in $form_state[original_form], etc all to no avail. The field doesn't change.

I also set one checkbox in the field at the start, so that I could find it in the $form and $form_state structures, changed where I found it to the new options array, and again, no change. I am setting $form_state[rebuild] to true, and even tried explicitly calling for the form to be rebuilt.



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