如何獲得對象的副本

Question

我有一個列表，類似於“ List <Block>”。 我想要的是獲取與列表中的塊相同的塊，而不是列表中的對象。 並用塊修改圓頂並獲得另一個。

但是問題是，在獲取了三次塊（列表的長度為3）之后，第四個塊已經被修改。 我嘗試了所有我知道的方法，甚至使用“ new”，它只是將對象添加到列表中，而不是同一對象。

那么如何解決呢？

這是我的一些代碼：

//This is the list which length is 3
private List<BlockType> blocks;

//At the beginning it was like this but not work
//private List<Block> blocks;

//In a function to get a block type randomly
int blockNum = rand.Next(0, 3); //rand is a Random type
this.cBlock = new Block(blocks[blockNum]); //cBlock is object which I use to do something about the block

//The class Block goes to
class Block
{
    private List<Rectangle> _block;
    public List<Rectangle> block
    {
        get { return _block; }
    }

    private int _blockNum;
    public int blockNum
    {
        get { return _blockNum; }
    }

    public Block()
    {

    }

    public Block(int blockNum, List<Rectangle> block)
    {
        this._block = block;
        this._blockNum = blockNum;
    }

    public Block(BlockType block)
    {
        this._block = block.block;
        this._blockNum = block.blockNum;
    }
}

//And the BlockType is what I tried but does not work
class BlockType
{
    private List<Rectangle> _block;
    public List<Rectangle> block
    {
        get { return _block; }
    }

    private int _blockNum;
    public int blockNum
    {
        get { return _blockNum; }
    }

    public BlockType()
    {

    }

    public BlockType(int blockNum, List<Rectangle> block)
    {
        this._block = block;
        this._blockNum = blockNum;
    }
}

Answer 1

編輯：

OP誤以為新的Block實例被從List<Block>拔出，因為List<Rectangle>沒有在復制構造函數中克隆，而是簡單分配，因此導致兩個唯一的Block實例引用相同的List<Rectangle> 。

在這種情況下，正確的副本構造函數為：

public Block(Block originalBlock)
{
    this._block = new List<Rectangle>(originalBlock.block);
    this._blockNum = originalBlock.blockNum;
}

在Rectangle類中需要類似的復制構造函數。

---

這應該為您工作：

public class Block
{
    private List<Rectangle> _block;
    public List<Rectangle> block
    {
        get { return _block; }
    }

    private int _blockNum;
    public int blockNum
    {
        get { return _blockNum; }
    }

    // Copy constructor
    public Block(Block originalBlock)
    {
        // IMPORTANT: This does not create a new List<Rectangle>! See EDIT
        this._block = originalBlock.block;

        this._blockNum = originalBlock.blockNum;
    }
}

用法：

Block originalBlock = new Block();

// Returns a new instance of Block with similar member data.
Block copiedBlock = new Block(originalBlock);

閱讀有關如何：編寫副本構造函數的信息（C＃編程指南）。 微軟文檔