圖案

Question

我無法映射這些類：

• 訂單
• 托盤
• 盒

它們一起形成的關係作文，詳見this wikipedia article。

類訂購的實例有幾個托盤對象，其中有幾個箱對象。

這是我現在有：

class Order 
{ 
    public Order(){} 
    private List<Pallet> _pallets = new List<Pallet>; 
    public Pallet Add_pallet() 
    { 
     Pallet new_pallet = new Pallet(this); 
     this._pallets.Add(new_pallet); 
     return new_pallet; 
    } 
    //...other properties and methods... 
} 

---

class Pallet 
{ 
    private Order _parent_order; 
    private List<Box> _boxes = new List<Box>; 
    public Pallet(Order parent_order) 
    { 
     _parent_order = parent_order; 
    } 
    public Box Add_Box() 
    { 
     Box new_box = new Box(this); 
     this._boxes.Add(new_box); 
     return new_box; 
    } 
    //...other properties and methods... 
} 

---

class Box 
{ 
    private Pallet _parent_pallet; 
    public Box(Pallet parent_pallet){} 
    //...other properties and methods... 
} 

所有盒必須屬於托盤和所有托盤必須屬於訂購。
我怎樣才能正確地執行這個可以避免這一點：

static class Program 
{ 
    static void Main() 
    { 
     Order myOrder = new Order(); 
     Pallet myPallet = new Pallet(myOrder); 
     //Now I have a Pallet that belongs to an Order, 
     //but the Order object is not aware of it 
    } 
} 

我應該使用嵌套類，還是有我丟失的東西更有用？

Answer 1

我會做這樣的：

public class Order 
{ 
    private List<Pallet> _pallets = new List<Pallet>; 
    internal void Add_pallet(Pallet pallet) 
    { 
     if (!this._pallets.Contains(pallet)) 
      this._pallets.Add(pallet); 
    } 
    //...other properties and methods... 
} 

public class Pallet 
{ 
    private Order _parent_order; 
    private List<Box> _boxes = new List<Box>; 
    public Pallet(Order parent_order) 
    { 
     if (parent_order = null) 
      throw ArgumentNilException("parent_order must not be null"); 
     _parent_order = parent_order; 
     _parent_order.Add_pallet(this); 
    } 
    //...other properties and methods... 
} 

麻生太郎。