定义处理派生类集合的基类方法

时间:2016-01-25 06:44:51

标签: c# inheritance covariance

我试图在我的基类中放置一个通用的 Add 方法,该方法适用于不同类型的类,所有类都实现 ICollection 。到目前为止这么好,我能够使用装箱/拆箱来实现我想要的,但我想知道是否有更好的方法来做到这一点。我对协变界面玩的很少,但没有更好的运气 - 甚至可以定义 IVariantCollection 吗?

这里有一些代码可以解释我尝试实现的目标:

public abstract class Device
{
    public string Name { get; set; }
    public abstract void Print();
}

public class Printer : Device { public override void Print() => Debug.WriteLine($"{Name} printer printout"); }

public class Xero : Device { public override void Print() => Debug.WriteLine($"{Name} xero printout."); }

public abstract class Factory
{
    public abstract IEnumerable<Device> DeviceCollection { get; }
    public abstract void Add(object added);
    public void ListDevices() { foreach (var item in DeviceCollection) Debug.WriteLine($"Device: {item.Name}"); }
}

public class PrinterFactory : Factory
{
    public List<Printer> Printers = new List<Printer>();
    public override IEnumerable<Device> DeviceCollection => Printers;

    public override void Add(object added) { Printers.Add((Printer)added); }
}

public class XeroFactory : Factory
{
    public ObservableCollection<Xero> Xeros = new ObservableCollection<Xero>();
    public override IEnumerable<Device> DeviceCollection => Xeros;

    public XeroFactory() { Xeros.CollectionChanged += (s, e) => Debug.WriteLine($"Device added: {e.NewItems[0]}"); }
    public override void Add(object added) { Xeros.Add((Xero)added); }
}

代码有效,但我不知道这个解决方案与对象 - 还有其他方法来定义添加方法,也许是基础上的通用方法类?

1 个答案:

答案 0 :(得分:3)

将通用Factory与基类约束

一起使用
public abstract class Factory<TDevice> where TDevice : Device
{
    public abstract IEnumerable<TDevice> DeviceCollection { get; }
    public abstract void Add(TDevice added);
    public void ListDevices() 
        { 
            foreach (var item in DeviceCollection) 
                Debug.WriteLine($"Device: {item.Name}"); 
        }
}

然后

public class PrinterFactory : Factory<Printer>
{
    public List<Printer> Printers = new List<Printer>();
    public override IEnumerable<Printer> DeviceCollection => Printers;

    public override void Add(Printer added) { Printers.Add(added); }
}