0

我正在研究一个通用的循环缓冲区，但是在涉及到复制构造函数时遇到了一个绊脚石（请参见下面的代码示例）。

using namespace System;

/// A generic circular buffer with a fixed-size internal buffer which allows the caller to push data onto the buffer, pop data back off again and provides direct indexed access to any element.
generic<typename T>
public ref class CircularBuffer
{
protected:
    array<T, 1>^ m_buffer; /// The internal buffer used to store the data.
    unsigned int m_resultsInBuffer; /// A counter which records the number of results currently held in the buffer
    T m_nullValue; /// The value used to represent a null value within the buffer

public:
    CircularBuffer(unsigned int size, T nullValue):
      m_buffer(gcnew array<T, 1>(size)),
      m_nullValue(nullValue),
      m_resultsInBuffer(0)
    {

    }

    /// <summary>
    /// Copy constructor
    /// </summary>
    CircularBuffer(const CircularBuffer^& rhs)
    {
        CopyObject(rhs);
    }

    /// <summary>
    /// Assignment operator.
    /// </summary>
    /// <param name="objectToCopy"> The Zph2CsvConverter object to assign from. </param>
    /// <returns> This Zph2CsvConverter object following the assignment. </returns>
    CircularBuffer% operator=(const CircularBuffer^& objectToCopy)
    {
        CopyObject(objectToCopy);
        return *this;
    }

protected:
    /// <summary>
    /// Copies the member variables from a Zph2CsvConverter object to this object.
    /// </summary>
    /// <param name="objectToBeCopied"> The Zph2CsvConverter to be copied. </param>
    void CopyObject(const CircularBuffer^& objectToBeCopied)
    {
        m_buffer = safe_cast<array<T, 1>^>(objectToBeCopied->m_buffer->Clone());
        m_nullValue = objectToBeCopied->m_nullValue; // <-- "error C2440: '=' : cannot convert from 'const T' to 'T'"
        m_resultsInBuffer = objectToBeCopied->m_resultsInBuffer;
    }
};

编译这个给了我error C2440: '=' : cannot convert from 'const T' to 'T'

通常，我会将它与我自己的 ref 类一起使用，其中包括指向托管和非托管内存的指针，因此如果复制整个缓冲区，则需要深度复制缓冲区的内容。

我在这里想念什么？为什么我不能从某种类型的东西复制到某种类型const T的东西T？

4

1 回答 1

1

“C++/CLI 并不真正支持 const”的持续传奇中的另一个条目。

C++/CLI 中的复制构造函数是 T(T%)。赋值运算符是 T% operator=(T%)。没有 const 也没有 ref。

看到它们使用的一个好地方是 vc/include/cliext，它是 STL/CLR 实现类的所在地。不要使用它们。

于 2012-11-01T13:08:38.627 回答