[英]Define base class method working on derived class collection
我正在嘗試在我的基類中放置一個通用的Add方法,它將適用於不同類型的類,所有類都實現了ICollection 。 到目前為止這么好,我能夠使用裝箱/拆箱來實現我想要的,但我想知道是否有更好的方法來做到這一點。 我對協變界面玩的很少,但沒有更好的運氣 - 甚至可以定義IVariantCollection ?
這里有一些代碼可以解釋我嘗試實現的目標:
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); }
}
代碼有效,但我不知道這個解決方案與對象有什么關系 - 是否有其他方法來定義Add方法,也許是基類中的通用方法?
使用具有基類約束的通用Factory
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); }
}
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