Laravel从第三个表返回属性

我有三个表：

products
product_types
product_categories

products属于product_types，product_types属于product_categories。

如何从product_categories访问列 products ？

产品类型型号：

class ProductTypes extends Eloquent {
    public function category() {
        return $this->belongsTo('ProductCategories');
    }
}

产品型号：

class Product extends Eloquent {
    protected $table = 'products';
    public function brands() {
        return $this->belongsTo('ProductBrands', 'brand_id', 'id');
    }
    public function ages() {
        return $this->belongsTo('ProductAges', 'age_id', 'id');
    }
    public function types() {
        return $this->belongsTo('ProductTypes', 'type_id', 'id');
    }
    public function images() {
        return $this->hasMany('ProductImages');
    }
    public function reviews() {
        return $this->hasMany('ProductReviews');
    }
    public function toArray() {
        $ar = $this->attributes;
        $ar['brand'] = $this->brand;
        $ar['age'] = $this->age;
        $ar['type'] = $this->type;
        return $ar;
    }
    public function getBrandAttribute() {
        $brands = $this->brands()->first();
        return (isset($brands->brand) ? $brands->brand : '');
    }
    public function getAgeAttribute() {
        $ages = $this->ages()->first();
        return (isset($ages->age) ? $ages->age : '');
    }
    public function getTypeAttribute() {
        $types = $this->types()->first();
        return (isset($types->type) ? $types->type : '');
    }
}

我试过：

$productData->types()->category()->category

但这给出了一个错误，指出该方法不存在。

对不起标题，想不出一个。