How can I set max selection for Yii2 ActiveForm dropDownList?

Question

I am creating a form with this:

<?= $form->field($model, 'job_category')
     ->dropDownList($jobCategoryDropDown, ['options' => $jobCategoryOptionArray, 'multiple' => 'multiple'])
     ->label('Ngành nghề - chuyên môn (Bắt buộc) <span class="help-required"> * </span>') ?>

How can I limit users to select a maximum of 3 or more values?

Answer 1

You can do it this way. Declare a validator function in the model.

public function limitSelection($attribute,$params)
{
if(count($this->$attribute)>3)
    {
        $this->addError($attribute,"You are only allowed to select 3 or less items for ".$attribute);      
     }
 }

Then declare the rules in the following way.

public function rules()

{       

    return [    

..................other rules...................... 

       ['job_category', 'required','message'=>"Select at least one item for {attribute}"],           

       ['job_category', 'limitSelection']
        ];
}