Question

对不起，我不知道我的问题如何表达，
我在C＃中有一些代码：

public class Cell
{
    public bool boo;
    public bool boo2;

    public int xPos;
    public int yPos;

    public Cell(int xPosition, int yPosition)
    {
        xPos = xPosition;
        yPos = yPosition;
    }

    public void SomeMethod()
    {
        boo = false;
        boo2 = true;
    }

    public void SomeMethod2()
    {
        boo = true;
        boo2 = false;
    }
}

我创建了一个这样的实例：

public static Cell[,] w;
public Cell c

w = new Cell[5,5]
...
//some other code

以上代码的结果是我可以从Cell Class访问方法和属性，我尝试在F＃中创建相同的代码

type Cell(xPosition:int,yPosition:int) = 

    let mutable m_boo = false
    let mutable m_boo2 = false

    //x and y position of cell in picture box
    let mutable xPosition = 0
    let mutable yPosition = 0


    new(xPosition,yPosition) = new Cell(xPosition,yPosition)
    new() = new Cell(0,0)

    member this.xPos with get() = xPosition
                     and set newX = xPosition <- newX
    member this.yPos with get() = yPosition
                     and set newY = yPosition <- newY
    member this.boo with get() = m_boo
                         and set newBoo = m_boo <- newBoo
    member this.boo2 with get() = m_boo2
                         and set newBoo2 = m_boo2 <- newBoo2
    member this.SomeMethod() = 
        this.boo <- false
        this.boo2 <- true
    member this.SomeMethod2() = 
        this.boo <- true
        this.boo2 <- false

我尝试创建实例：

let worldGrid:Cell[,] = Array2D.zeroCreate 5 5
worldGrid.[0,0].SomeMethod2()

编译代码的结果是：

System.NullReferenceException：未将对象引用设置为对象的实例

在我的代码中是不正确的，还是我做错了？希望阅读代码有助于理解我的问题。

Answer 1

Array2D.zeroCreate 5 5确实创建了25个Cell类的空实例。如果要使用默认值初始化它们，则应使用：

let worldGrid = Array2D.init 5 5 (fun _ _ -> Cell())

否则您必须在访问其方法和字段之前将矩阵的每个元素分配给Cell实例。

另一个问题是可变值xPosition和yPosition被初始化为0有关构造函数的参数。此外，这些可变值和类的参数应具有不同的名称，以避免阴影和混淆。该课程可能如下所示：

type Cell(xPos:int, yPos:int) = 

    let mutable m_boo = false
    let mutable m_boo2 = false

    // x and y position of cell in picture box
    let mutable xPosition = xPos
    let mutable yPosition = yPos

    // ...

如何创建2D数组但内容是一个类？

1 个答案: