Question

我似乎对对象的引用有一个意想不到的问题。我的代码有一个草稿：

// file 1
List<A> list1;
List<B> list2 = function(list1);
//file 2
public static List<B> function(List<A> input)
{
    list<B> output = new List<B>();
    for (int i ...)
    {
        output.Add(new B(input[i]));
    {
    return output;
}
// file 1
list1[1].FieldOfAObject = 10; // I change an object from list1
WriteLine(list2[1].objectA.FieldOfAObject); // it is not changed

在我看来，由于list1是一个类而A是一个类，并且它们是通过引用传递的，因此在function中创建并分配给list2的类型B的对象应该保留关于list1的对象的参考。

修改真实代码：

public void PrintCylinder(Camera camera, Cylinder cylinder, Bitmap Bitmap, double bitmapWidth, double bitmapHeight, PrintArguments pa)
    {
        ...
        List<AffineCoordinates> verticesToPritOnScreen = new List<AffineCoordinates>(); // out list1
        foreach (var vertex in cylinder.Mesh.MeshVertices)
        {
            AffineCoordinates newVertex = PVM * vertex;
            verticesToPritOnScreen.Add(newVertex); // list1 is being filled here
        }

        List<Face> FaceList = MeshGridGenerator.GenerateCylinderGrid(verticesToPritOnScreen, cylinder.D); // our list2

// CHANGES BENEATH ARE NOT VISIBLE IN FaceList objects
        for (int i = 0; i < verticesToPritOnScreen.Count; ++i)
        {
            // project to NDC
            verticesToPritOnScreen[i] = verticesToPritOnScreen[i] / verticesToPritOnScreen[i].W;
            // project to screen space
            verticesToPritOnScreen[i].X = (verticesToPritOnScreen[i].X + 1) * bitmapWidth / 2;
            verticesToPritOnScreen[i].Y = (verticesToPritOnScreen[i].Y + 1) * bitmapHeight / 2;
            verticesToPritOnScreen[i].Z = (verticesToPritOnScreen[i].Z + 1) / 2;
            verticesToPritOnScreen[i].W = 1;
        }

        ...
    }
// our function (from MeshGridGenerator class)
public static List<Face> GenerateCylinderGrid(List<AffineCoordinates> vertices, int D)
    {
        List<Face> FaceList = new List<Face>();

        for (int i = 1; i <= D; ++i)
        {
            // upper base
            FaceList.Add(new Face(vertices[0], vertices[i], vertices[i % D + 1]));
            // bottom base
            FaceList.Add(new Face(vertices[vertices.Count - 1], vertices[i % D + 1 + D], vertices[i + D]));
            // side wall's upper triangle
            FaceList.Add(new Face(vertices[i], vertices[i + D], vertices[i % D + 1]));
            // side wall's bottom triangle
            FaceList.Add(new Face(vertices[i % D + 1], vertices[i + D], vertices[i % D + 1 + D]));
        }

        return FaceList;
    }
// our B class
public class Face
{
    public AffineCoordinates[] vertices;

    public bool AreVerticesClockwise
    {
        get
        {
            double sum = 0.0;
            for (int i = 0; i < 3; ++i)
            {
                sum += (vertices[(i + 1) % 3].X - vertices[i].X) * (vertices[(i + 1) % 3].Y + vertices[i].Y);
            }
            return sum < 0;
        }
    }

    public Face(params AffineCoordinates[] ver)
    {
        vertices = new AffineCoordinates[3];
        vertices[0] = ver[0];
        vertices[1] = ver[1];
        vertices[2] = ver[2];
    }
}

我知道这是很多颂歌，这就是为什么我不想发布它。

Answer 1

这段代码打印'20'，这是我认为你想要的？

 public class A
 {
      public int Value;
 }

 public class B
 {
      public A objectA;
      public B(A obj)
      {
            objectA = obj;
      }
 }
 class Program
 {
      public static List<B> function(List<A> input)
      {
            List<B> output = new List<B>();
            foreach  (var i in input)
            {
                 output.Add(new B(i));
            }
            return output;
      }
      static void Main(string[] args)
      {
            List<A> listA = new List<A>();
            listA.Add(new A { Value = 10 });
            List<B> listB = function(listA);
            listA[0].Value = 20;
            Console.WriteLine(listB[0].objectA.Value);
      }
 }

将列表作为参数传递

1 个答案: