Check a form field for duplicates before saving

Question

I have a custom component where the user can add some data. Here are the two relevant fields:

<field 
    name="title" 
    type="text" 
    label="Title" 
    description="Please enter a title" 
    required="true" 
/>
<field 
    name="alias" 
    type="text" 
    label="Alias" 
    description="Please enter an unique alias" 
    required="true" 
/>

I am currently using the standard 'save' method to save the form data. But the problem obvious is that it is saving duplicate alias items. Where and how will I add a check to ensure that the alias is not in use (just like with Menu Item or Article).

Answer 1

The best place is your table class before storing data. For example below code in store function of table class.

public function store ($updateNulls = false)
{
    if ($table->load(array('alias' => $this->alias, 'catid' => $this->catid)) && ($table->id != $this->id || $this->id == 0))
    {
        $this->setError(JText::_('COM_MYCOMPONENT_DATABASE_ERROR_UNIQUE_ALIAS').'| Alias: '.$this->alias);
        return false;
    }

    return parent::store($updateNulls);
}

Answer 2

I followed the answer and came up with the following:

  public function save($data){
        $table = $this->getTable();
        $table->load(array('alias' => $data['alias']));

        if (($table->alias == $data['alias']) && $table->id != $data['id'])
        {
            $this->setError(JText::_('COM_MYCOMPONENT_ALIAS_ALREADY_EXISTS').'| Alias: ' . $data['alias']);
            return false;
        }
        $save = parent::save($data);
    }