cakephp Model validation error message not displaying in hasOne association

Question

i want to do model validation with association in a single form. i have two tables users(parent table) and user_details(child

Answer 1

You're trying to patch your details entity with the wrong data ($this->request->getData()). But really, there is no need to create, patch and save a separate entity in your add function, because the first level of associations will be handled transparently for you. This should work just fine:

public function add() {
    $user = $this->Users->newEntity();
    if ($this->request->is('post')) {
        $user = $this->Users->patchEntity($user, $this->request->getData());
        if ($this->Users->save($user)) {
            $this->Flash->success(__('The user has been saved.'));
            return $this->redirect($this->referer());
        } else {
            $this->Flash->error(__('The user could not be saved. Please, try again.'));
        }
    }
    $this->set(compact('user'));
}

Or, at least, it should once you correct the field names from the details entity to include "user_detail.", as @ndm said; your HTML above is still showing $this->Form->control('address',...) instead of $this->Form->control('user_detail.address',...), though it also includes fields for city and state, which aren't in your screen shot, so it's unclear what your current version might look like.