board.x = BOARD_X_OFFSET;
board.y = BOARD_Y_OFFSET;
board.w = BOARD_WIDTH;
board.h = BOARD_HEIGHT;
PassiveBlock *passiveBlocks;
passiveBlocks = new PassiveBlock[ BOARD_WIDTH ][ BOARD_HEIGHT ];
for( int X = 0; X < board.w ; X++ )
{
for( int Y = 0; Y < board.h; Y++ )
{
passiveBlocks[ X ][ Y ].Init( X + board.x, Y + board.y );
}
}
I need help with class arrays
Author
(correct me if I mix up any terms, still learning much of the basics of programming)
I'm trying to set up an array of 10*20 classes,
the PassiveBlock declaration and definition is in another .h and .cpp file respectively.
I'm using VC++ now, this worked in DevC++, the code is copied from DevC++ and it worked until VC++ registered a change in this part and wanted to recompile. My guess is that VC++ don't like it this way.
In my C++ book this should work for arrays with one [] but I'm probably messing it up with multiple []'s.
Thanks in advance for any help.
new can only allocate one-dimensional arrays. You will have to handle multiple dimensions yourself.
I would personally suggest either using std::vector twice, or boost::multi_array with two dimensions once.
I would personally suggest either using std::vector twice, or boost::multi_array with two dimensions once.
The correct way to create your two-dimensional dynamic array in C++ is to allocate a one-dimensional array of PassiveBlock pointers, then iterate (loop) over each element of that array and for each one allocate another array of PassiveBlocks.
Generally speaking, two-dimensional arrays aren't always your friend, either use boost::multi_array or use a one-dimensional array and access it like a two-dimensional array:
You can still do better than that and use std::vector which is recommended instead of using new[]:
If PassiveBlock is fitted with a constructor that fullfills the same job as the Init method then you could also ditch Init and do it this way:
As your problem partially demonstrates, using new[] and delete[] (especially for multi-dimensional arrays) is error prone, using the correct RAII container for the job is almost always better [smile]
Hope that was of some help.
Generally speaking, two-dimensional arrays aren't always your friend, either use boost::multi_array or use a one-dimensional array and access it like a two-dimensional array:
passiveBlocks = new PassiveBlock[BOARD_WIDTH * BOARD_HEIGHT]; for( int X = 0; X < board.w ; X++ ) { for( int Y = 0; Y < board.h; Y++ ) { passiveBlocks[ Y * BOARD_WIDTH + X ].Init( X + board.x, Y + board.y ); } } /* do stuff */ delete[] passiveBlocks; // Don't forget this!You can still do better than that and use std::vector which is recommended instead of using new[]:
std::vector<PassiveBlock> passiveBlocks( BOARD_WIDTH * BOARD_HEIGHT ); for( int X = 0; X < board.w ; X++ ) { for( int Y = 0; Y < board.h; Y++ ) { passiveBlocks[ Y * BOARD_WIDTH + X ].Init( X + board.x, Y + board.y ); } }If PassiveBlock is fitted with a constructor that fullfills the same job as the Init method then you could also ditch Init and do it this way:
std::vector<PassiveBlock> passiveBlocks; passiveBlocks.reserve( BOARD_WIDTH * BOARD_HEIGHT ); for( int Y = 0; Y < board.h ; Y++ ) { for( int X = 0; X < board.w; X++ ) { passiveBlocks.push_back( PassiveBlock(X + board.x, Y + board.y) ); } }As your problem partially demonstrates, using new[] and delete[] (especially for multi-dimensional arrays) is error prone, using the correct RAII container for the job is almost always better [smile]
Hope that was of some help.
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