code: public function setField(SelectorInterface $selector, $value, $position=false)
      {
          $success   = false;
          $_position = 0;
          for ($i = 0, $count = count($this->widgets); $i < $count; $i++) {
              if ($selector->isMatch($this->widgets[$i])) {
                  $_position++;
                  if ($position === false or $_position === (int) $position) {
                      if ($this->widgets[$i]->setValue($value)) {
                          $success = true;
                      }
                  }
              }
          }
  
          return $success;
      }
docs: Sets a widget value within the form.
  
  @param $selector   Criteria to apply.
  @param string $value Value to input into the widget.
  
  @return bool                   True if value is legal, false otherwise.
  If the field is not present, nothing will be set.