C维二维数组存在问题

Question

I have searched this website and Google, and haven't really found anything that solves my problem. I am trying to write a game right now, and this game contains a map of terrain tiles that the player can move across. I want to store the tiles in a 10x10 array, but I am having trouble initializing the array.

I can initialize the first dimension of the array, but the error lies within initializing the second dimension within the first for loop.

Here is what my code looks like:

//tile on the "map"
struct tile
{
    char type;
    bool isWall;
};

void initializeMap(tile * map)
{
  int index1, index2;

  for(index1 = 0; index1 < 10; index1++)
  {
    map[index1] = new tile[10];

    for(index2 = 0; index2 < 10; index2++)
    {

    }
  }
}

int main()
{
    tile * tileMap = new tile[10];
    initializeMap(tileMap);

    return 0;
}

I am getting this error:

C:\Users\----\Desktop\TextGame.cpp||In function 'void initializeMap(tile*)':|
C:\Users\----\Desktop\TextGame.cpp|39|error: no match for 'operator=' in '*(map + ((unsigned int)(((unsigned int)index1) * 2u))) = (tile*)operator new [](20u)'|
C:\Users\----\Desktop\TextGame.cpp|9|note: candidates are: tile& tile::operator=(const tile&)|
||=== Build finished: 1 errors, 0 warnings ===|

Answer 1

You are trying to set an actual object to a pointer with the command:

map[index1] = new tile[10];

map is a tile* . However, map[index1] is a deferenced tile* making it actually a tile which cannot equal a tile* which new tile[10] gives you.

Therefore, your code will work better as:

struct tile {
   char type;
   bool isWall;
};

/**
 * Initialize the map
 * @param map The array of tile pointers
 */
void initializeMap(tile** map) {
   int index1, index2;
   for (index1 = 0; index1 < 10; index1++) {

      // Set each element of the tile* array 
      // to another array of tile pointers
      map[index1] = new tile[10];

      for (index2 = 0; index2 < 10; index2++) {
         // Do Something
      }
   }
}

int main() {
   // Create a pointer to a set of tile pointers
   tile** tileMap = new tile*[10];
   // Pass it to the initializer
   initializeMap(tileMap);
   return 0;
}

Answer 2

NOTE: Technically, thats not a 2-dimensional array, is an array of arrays of structs.

Said that, that note reflects the problem of your code: You have an array of arrays, so the first allocation should allocate an array which contents are pointers to other arrays :

tile** tilemap = new tile*[10];

for( std::size_t i = 0 ; i < 10 ; ++i )
    tilemap[i] = new tile[10];

....

//Dealocation at program finish:

for( std::size_t i = 0 ; i < 10 ; ++i )
    delete tilemap[i];

delete tilemap;

However your code could be improved if you use standard containers, like std::vector , instead of manual memory management, which is error-prone:

std::vector<std::vector<tile>> tilemap( 10 );

for( std::size_t i = 0 ; i < 10 ; ++i )
    tilemap.emplace_back( 10 );

Answer 3

I recommend using a std::vector of shared pointers to tiles. This will allow you to have different tiles and store them into the vector:

struct Tile; // As you declared it.

struct Water_Tile : public Tile;
struct Mountain_Tile : public Tile;
struct Desert_Tile : public Tile;

// ...
typedef std::vector< boost::shared_ptr<Tile> > Tile_Container;

//...
Tile_Container    my_world(10 * 10);

// ...
my_world[20] = new Water_Tile;

A nice advantage of the shared pointer is that it handles memory management (deletion) for you.