c# – 在界面中使用泛型

更新：

海因兹是对的. AutoCAD Polyline是引用类型,而不是结构.好点子.但我简化了场景,因为我在实际应用程序中处理的是一个AutoCAD对象,它是struct.所以请将两者都视为struct而不是引用类型.

我正在寻找正确的方法来应对这种情况,如果有人能够阐明或帮助我更好地理解,我将不胜感激.

数据访问层中有一个接口,有两个实现来处理两个不同的提供程序：AutoCad和Sketchup API.

interface IEntity
{
    void object GetPoly();
    void void   InsertPoly(object poly);
}

class AutocadEntity
{
    void object GetPoly()
    {
         //calling Autocad APIs
         return Autocad Polyline object
    }
    void InsertPoly(object poly){...}
}

GetPoly的Autocad实现将返回Polyline对象,因为这是在Autocad API中定义为折线,而Sketchup将返回Face对象.

我已经将返回类型(和参数)定义为对象来处理这些不同的类型.成本是拳击/拆箱发生时的性能问题.并且它更大胆地显示返回/参数是object []的位置.

我首先想知道方法返回/参数类型泛型是解决方案,但我认为它不会是因为实现是特定于类型的.

解决方法:

尝试使用adapter pattern将PolyLine和Face类型调整为您希望使用的单一类型.例如：

public abstract class BasePoly
{
    public abstract double X { get; set; }
    public abstract double Y { get; set; }
    public abstract double Width { get; set; }
    public abstract double Height { get; set; }
}
public abstract class BasePoly<T> : BasePoly
{
    public T poly { get; private set; }
    protected BasePoly(T poly) { this.poly = poly; }
}

public class PolyLineAdapter : BasePoly<PolyLine>
{
    public PolyLineAdapter(PolyLine poly) : base(poly) {}
    // override abstracts and forward to inner PolyLine instance at 'this.poly'

    public override double X { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }

    public override double Y { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }

    public override double Width { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }

    public override double Height { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }

}

public class FaceAdapter : BasePoly<Face>
{
    public FaceAdapter(Face poly) : base(poly) {}
    // override abstracts and forward to inner Face instance at 'this.poly'

    public override double X { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }

    public override double Y { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }

    public override double Width { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }

    public override double Height { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }


}

interface IEntity
{
    BasePoly GetPoly();
    void   InsertPoly(BasePoly poly);
}

public abstract class Entity<TEntity> : IEntity
    where TEntity : BasePoly
{
    public BasePoly GetPoly()
    {
        return this.GetExternalPoly();
    }
    public abstract TEntity GetExternalPoly();
    public void InsertPoly(BasePoly poly)
    {
        this.InsertExternalPoly((TEntity) poly);
    }
    public abstract void InsertExternalPoly(TEntity poly);
}

public class AutocadEntity : Entity<PolyLineAdapter>
{
    public override PolyLineAdapter GetExternalPoly()
    {
        throw new NotImplementedException();
    }
    public override void InsertExternalPoly(PolyLineAdapter poly)
    {
        throw new NotImplementedException();
    }
}

public class SketchupEntity : Entity<FaceAdapter>
{
    public override FaceAdapter GetExternalPoly()
    {
        throw new NotImplementedException();
    }
    public override void InsertExternalPoly(FaceAdapter poly)
    {
        throw new NotImplementedException();
    }
}

// fills for third party classes
public class PolyLine {}
public class Face {}

使用adapter pattern,您提供代理层以使两个第三方类型符合您要使用的类型.

请记住,此设计假设您一次只能使用一种类型的第三方引擎.如果您将同时使用两个引擎,请进行以下更改：

public class BasePoly
{
    public double X { get; set; }
    public double Y { get; set; }
    public double Width { get; set; }
    public double Height { get; set; }
}

interface IEntity
{
    BasePoly GetPoly();
    void InsertPoly(BasePoly poly);
}

public abstract class Entity : IEntity
{
    public abstract BasePoly GetPoly();
    public abstract void InsertPoly(BasePoly poly);
}

public class AutocadEntity : Entity
{
    public override BasePoly GetPoly()
    {
        // retrieve external type, convert it to BasePoly and return that
        throw new NotImplementedException();
    }
    public override void InsertPoly(BasePoly poly)
    {
        // convert BasePoly to external type and insert that
        throw new NotImplementedException();
    }
}

public class SketchupEntity : Entity
{
    public override BasePoly GetPoly()
    {
        // retrieve external type, convert it to BasePoly and return that
        throw new NotImplementedException();
    }
    public override void InsertPoly(BasePoly poly)
    {
        // convert BasePoly to external type and insert that
        throw new NotImplementedException();
    }

}

// fills for third party classes
public class PolyLine {}
public class Face {}

此外,如果您担心适配器装箱或转换操作的成本(在您实际测量并确定是否需要优化之前我不会这样做),那么您可以将适配器模式应用于使用IEntity的调用者而不是PolyLineAdapter / FaceAdapter或AutocadEntity / SketchupEntity类型本身.基本上,构建一个插件引擎.您可以使用泛型来抽象两个实现之间的常见习语.

这是一个dotnetfiddle示例：https://dotnetfiddle.net/UsFPM7

标签：c,boxing,unboxing,generics
来源： https://codeday.me/bug/20190516/1117093.html