framework/behaviors/SluggableBehavior.php
protected function validateSlug($slug)
    {
        /* @var $validator UniqueValidator */
        /* @var $model BaseActiveRecord */
        $validator = Yii::createObject(array_merge(
            [
                'class' => UniqueValidator::className(),
            ],
            $this->uniqueValidator
        ));

        $model = clone $this->owner;
        $model->clearErrors();
        $model->{$this->slugAttribute} = $slug;

        $validator->validateAttribute($model, $this->slugAttribute);
        return !$model->hasErrors();
    }
protected function validateSlug($slug)
    {
        /* @var $validator UniqueValidator */
        /* @var $model BaseActiveRecord */
        $validator = Yii::createObject(array_merge(
            [
                'class' => UniqueValidator::className(),
            ],
            $this->uniqueValidator
        ));

        $model = clone $this->owner;
        $model->clearErrors();
        $model->{$this->slugAttribute} = $slug;

        $validator->validateAttribute($model, $this->slugAttribute);
        return !$model->hasErrors();
    }
Checks if given slug value is unique.
@param string $slug slug value
@return bool whether slug is unique.