Laravel / Eloquent三重模型多对多关系

Question

我正在尝试用Eloquent（Laravel 5.5）写作：

我的表格结构如下

1. 产品
2. 颜色
3. 尺寸
4. colour_product - 数据透视表

我有一系列产品和颜色（多对多）。对于每种产品 - 颜色对有多种尺寸。我需要像'colour_product_sizes'这样的东西。请使用Laravel Eloquent建议一种方法。

Product.php（产品型号）

    <?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Product extends Model
{
   use \Dimsav\Translatable\Translatable;
   public $translatedAttributes = ['name','short_description'];


   public function colours()
   {
    return $this->belongsToMany(Colour::class,'colour_product')->withTimestamps();
   }

   public function sizes()
   {
    return $this->belongsToMany(Size::class);
   } 


}

?>

Colour.php（颜色模型）

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Colour extends Model
{
   use \Dimsav\Translatable\Translatable;

   public $translatedAttributes = ['name'];
   protected $fillable = ['code'];

   public function products()
   {
    return $this->belongsToMany(Product::class);
   }
}
?>

Size.php（尺寸模型）

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Size extends Model
{

   use \Dimsav\Translatable\Translatable;

   public $translatedAttributes = ['name','short_name','extra'];    
   protected $fillable = ['code'];

   public function products()
   {
    return $this->belongsToMany(Product::class);
   }

}
?>

colour_product表架构

1   id  int(10) UNSIGNED    
2   product_id  int(10) UNSIGNED    
3   colour_id   int(10) UNSIGNED    
4   created_at  datetime    
5   updated_at  datetime