c# - 在 C++ 中的两个类之间共享(QList 的)实例

Question

从 C# 到 Qt，我无法理解如何正确翻译以下常见习语 (C#):

class Customer {
  public property List<Address> Addresses { get; }
}

class AnotherClass {
  public void SetAsShipping(List<Address> addresses) {
    foreach(var address in addresses)
      if (address.IsMatch(_shipping))
        address.IsShipping = true;    // This is the important part
  }
}

var cust = new Customer();
var another = new AnotherClass();

another.SetAsShipping(cust.Addresses);

我有以下 C++:

class Customer {
  public:
    QList<Address> addresses() const { return _addresses; }
  private:
    QList<Address> _addresses;
};

class AnotherClass {
public:
  void setAsShipping(QList<Address> addresses);
};

AnotherClass::setAsShipping(QList<Address> addresses) {
  QList<Address>::iterator address;

  for (address = addresses->begin(); address != addresses->end(); ++address)
    if (address->isMatch(_shipping))
      address->setIsShipping(true);    // This is modifying a copy :(
}

Customer cust;
AnotherClass another;

another.setAsShipping(cust.addresses());

我知道我可以将 _addresses 作为引用返回，然后通过引用传递它，但显然这会导致问题，因为我的 Customer 实例可能会在对 _addresses 的引用之前超出范围，这将导致“悬空引用”。我从搜索中发现了很多。我没有找到的是应该做什么。显然，有一种标准的 C++ 方法可以执行此类操作，但我的大脑一直停留在托管代码模式，以至于它不会跳出来。我应该如何编写这段代码，以便 AnotherClass 可以修改地址列表？

Answer 1

在您的 C# Customer 类中，Addresses 只是公共(public)属性，您也可以在 C++ 中这样做，但这显然不是一个好的设计。

class Customer {
  public:
     QList<Address> _addresses;
};

AnotherClass::setAsShipping(QList<Address>& addresses) {
  for (QList<Address>::iterator address = addresses->begin(); 
       address != addresses->end(); ++address)
  {    
    if (address->isMatch(_shipping)) {
      address->setIsShipping(true);    // Now modify the real object
    } 
  }
}

为了以更好的方式做到这一点，让我们重新考虑您的 C# 设计。

1.为什么是List<Address> Addresses公开？

2.SetAsShipping 真的应该属于另一个类吗？看起来它属于 Customer 类？

3.进一步增强，可以使用Qlist算法代替for循环来查找地址吗？

class Customer
{
public:
    void setAsShipping(const Address& address)
    {
        for (QList<Address>::iterator address = addresses->begin(); 
        address != addresses->end(); ++address)
        {    
            if (address->isMatch(_shipping)) {
                address->setIsShipping(true);    // Now modify the real object
            } 
        }
    }
private:
  QList<Address> _addresses;
};

customer cust;
AnotherClass another;

cust.setAsShipping(another.address()); 

现在还存在悬空引用问题吗？