Question

这是我第一次使用Boost，我正在尝试创建类Blocks的多列，它存储在Chunk类中。所以每个Chunk由（BLOCKS_PER_CHUNK x BLOCKS_PER_CHUNK x BLOCKS_PER_CHUNK）块数组成，与Minecraft的方式基本相同。目前我正在尝试使用两个不同的构造函数初始化此数组，其中一个构造函数将stl向量作为输入，另一个构造函数使用“C样式向量”。

Block只有一个布尔值来检查它是否处于活动状态（默认值为false），块类型（基本上是枚举）以及变量的getter和setter。

Chunk的标题如下：

#pragma once

#include "Block.h"
#include <vector>
#include "Block.h"
#include "boost/multi_array.hpp" // Multi dimensional array

#define BLOCKS_PER_CHUNK 16

class Chunk
{
public:
    Chunk();
    Chunk(std::vector<Block>& blocks);
    Chunk(Block* blocks); // Assumes you have a vector of the correct size
    virtual ~Chunk();

    void Update(float timeSinceLastUpdate);

private:
    //BlockVec3D blocks;
    //BlockArray blocks;
    typedef boost::multi_array<Block, BLOCKS_PER_CHUNK> blockArray;
    typedef blockArray::index blockArrayIndex;

    blockArray m_blocks;
};

问题功能如下：

Chunk::Chunk(std::vector<Block>& blocks):
    m_blocks(boost::extents[BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK])
{
    assert(blocks.size() == BLOCKS_PER_CHUNK * BLOCKS_PER_CHUNK * BLOCKS_PER_CHUNK && "Number of blocks and size of the chunk do not match");
    for(unsigned i = 0; i < BLOCKS_PER_CHUNK; ++i)
    {
        for(unsigned j = 0; j < BLOCKS_PER_CHUNK; ++j)
        {
            for( unsigned k = 0; k < BLOCKS_PER_CHUNK; ++k)
            {
                m_blocks[i][j][k] = blocks[i + BLOCKS_PER_CHUNK * (j + BLOCKS_PER_CHUNK * k) ];
            }
        }
    }
}

Chunk::Chunk(Block* blocks)
{
    for(unsigned i = 0; i < BLOCKS_PER_CHUNK; ++i)
    {
        for(unsigned j = 0; j < BLOCKS_PER_CHUNK; ++j)
        {
            for( unsigned k = 0; k < BLOCKS_PER_CHUNK; ++k)
            {
                m_blocks[i][j][k] = blocks[i + BLOCKS_PER_CHUNK * (j + BLOCKS_PER_CHUNK * k) ];
            }
        }
    }
}

在尝试编译此代码时，我收到错误，例如shape，num_dimensions，begin和end不是Block的成员。似乎boost有自己的静态断言的味道，检查必需的字段，当找不到它们时，它会产生编译错误。显然，boost试图将输入值视为一维子阵列，当它无法找到其完整性检查所需的字段时（例如两个“子阵列”具有相同数量的维度），它会触发错误。

容器的手册似乎没有解决这个特定的问题，我不相信我偶然会创建一个多阵列视图。另外，将左侧的指数投入到 boost::multi_array<Block, BLOCKS_PER_CHUNK>::index似乎没有任何区别。正如我所提到的，我仍然很擅长提升。这样做的正确方法是什么？

Answer 1

错误是m_blocks初始化的方式。您将BLOCKS_PER_CHUNK值指定为16，但仅将其初始化为3维数组。

#include <iostream>
#include <vector>
#include <boost/multi_array.hpp>
#include <cassert>

#define BLOCKS_PER_CHUNK 3

struct Block{


};


struct Chunk{


  typedef boost::multi_array<Block, BLOCKS_PER_CHUNK> array_type;
  typedef array_type::index index;
  array_type m_blocks;

  Chunk(std::vector<Block>& blocks):
    m_blocks(boost::extents[BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK])
  {
    assert(blocks.size() == BLOCKS_PER_CHUNK * BLOCKS_PER_CHUNK * BLOCKS_PER_CHUNK && "Number of   
blocks and size of the chunk do not match");
    for(unsigned i = 0; i < BLOCKS_PER_CHUNK; ++i)
    {
      for(unsigned j = 0; j < BLOCKS_PER_CHUNK; ++j)
      {
for( unsigned k = 0; k < BLOCKS_PER_CHUNK; ++k)
        {
          m_blocks[i][j][k] = blocks[i + BLOCKS_PER_CHUNK * (j + BLOCKS_PER_CHUNK * k) ];
        }
      }
    }
  }

  Chunk(Block* blocks)
  {
    for(unsigned i = 0; i < BLOCKS_PER_CHUNK; ++i)
    {
      for(unsigned j = 0; j < BLOCKS_PER_CHUNK; ++j)
      {
        for( unsigned k = 0; k < BLOCKS_PER_CHUNK; ++k)
        {
          m_blocks[i][j][k] = blocks[i + BLOCKS_PER_CHUNK * (j + BLOCKS_PER_CHUNK * k) ];
        }
      }
    }
  }

};

int main(){
 return 0;
}

上面的示例正确编译，因为BLOCKS_PER_CHUNK和m_blocks初始化匹配。比如说BLOCKS_PER_CHUNK被定义为4，那么m_blocks应该被初始化为：

  #define BLOCKS_PER_CHUNK 4

struct Block{


};


struct Chunk{

  typedef boost::multi_array<Block, BLOCKS_PER_CHUNK> array_type;
  typedef array_type::index index;
  array_type m_blocks;

  Chunk(std::vector<Block>& blocks):
//initialization has to change if BLOCKS_PER_CHUNK changes
    m_blocks(
boost::extents[BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK])
  {

    assert(blocks.size() == BLOCKS_PER_CHUNK * BLOCKS_PER_CHUNK * BLOCKS_PER_CHUNK && "Number of   blocks and size of the chunk do not match");
    for(unsigned i = 0; i < BLOCKS_PER_CHUNK; ++i)
    {
      for(unsigned j = 0; j < BLOCKS_PER_CHUNK; ++j)
      {
        for( unsigned k = 0; k < BLOCKS_PER_CHUNK; ++k)
        {
//correct value assignment has to be taken care when BLOCKS_PER_CHUNK change
          m_blocks[i][j][k][k] = blocks[i + BLOCKS_PER_CHUNK * (j + BLOCKS_PER_CHUNK * k) ];
        }
      }
    }
  }

};

如果你想要16个宽，16个高和16个深的块集合，那么代码应该是这样的：

  #define BLOCKS_PER_CHUNK 16
  #define DIMENSION 3

struct Block{


};


struct Chunk{

typedef boost::multi_array<Block, DIMENSION> array_type;
  typedef array_type::index index;
  array_type m_blocks;

  Chunk(std::vector<Block>& blocks):
//initialization has to change if BLOCKS_PER_CHUNK changes
    m_blocks(
boost::extents[BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK][BLOCKS_PER_CHUNK])
  {

    assert(blocks.size() == BLOCKS_PER_CHUNK * BLOCKS_PER_CHUNK * BLOCKS_PER_CHUNK && "Number of   blocks and size of the chunk do not match");
    for(unsigned i = 0; i < BLOCKS_PER_CHUNK; ++i)
    {
      for(unsigned j = 0; j < BLOCKS_PER_CHUNK; ++j)
      {
        for( unsigned k = 0; k < BLOCKS_PER_CHUNK; ++k)
        {
//correct value assignment has to be taken care when BLOCKS_PER_CHUNK change
          m_blocks[i][j][k] = blocks[i + BLOCKS_PER_CHUNK * (j + BLOCKS_PER_CHUNK * k) ];
        }
      }
    }
  }

};

array_type typedef中的第二个参数指定数组的维度，在您希望它为3的情况下，然后将typedef修改为：

typedef boost::multi_array<Block, DIMENSION> array_type; //where DIMENSION is 3

如何创建特定类的boost多重阵列？

1 个答案: