Remove field data in submit function

Question

Drupal 7. On form validate, I want to:

• check the value of one of the form fields [field-1]
• based on that value, completely remove another field [field-2] together with its values, from the form

If it makes any difference, [field-2] is a multiple-value entity-reference field.

I think I need to do something like --- get hold of $form_state['values']['field_2'] and set it so that it is in the same state it is before any data was entered by the user.

Am I on the right lines? I haven't been able to find examples or documentation on this.

EDIT:

This is what worked for me in the end:

In the submit function (not the validate function):

// Start with a clean array for the field we want to change.
$form_state['values']['field_2'] = array();
// Restore the array values that correspond to 'empty' for this field.
// In my case this was as follows:
$form_state['values']['field_2']['und'][0]['target_id'] = '';

Answer 1

Short answer is yes you are on the right track. Altering form values on validation can get a little tricky and complex depending on the form. You might want to check out form_set_value if you haven't already.