CODEWITHSUNDEEP
arraysactionscript-3multidimensional-array
user2072135
user2072135

Reputation: 59

Having trouble understanding multidimensional arrays in as3

Let's say I have some code like:

private function makeGrid():void
    {
        _grid = new Array();

        for(var i:int = 0; i < stage.stageWidth / GRID_SIZE; i++)
        {
            _grid[i] = new Array();

            for(var j:int = 0; j < stage.stageHeight / GRID_SIZE; j++)
            {
                _grid[i][j] = new Array();
            }
        }
    }

I don't quite understand what's going on. I get that in the first for loop it determines the number of columns needed, and in the second it determines rows, but I don't get why I'm making arrays out of _grid[i] and _grid[i][j].

For instance, _grid[i] = new Array(); get's called 16 times (800px/50px), so that would make 16 arrays right? Why do I need those if the second for loops is already calculating the amount of rows I need?

Upvotes: 0

Views: 95

Answers (1)

Bennett Keller
Bennett Keller

Reputation: 1714

I'm just going to elaborate on what has already been commented. Let's say that you are creating a 2D grid formed of rows and columns and you wanted to store some sort of data at each "cell" or specified index of the grid.

The first step is to create the first array to hold either the rows or columns (which you choose first doesn't really matter as you can adjust the for loops either way).

The first for loop creates a new row, then in the next inner loop you fill all the columns of that row (if we had chosen columns to be created first then we would fill all the rows of the columns). In this case the inner loop is creating all the columns with another array (making it a 3-dimensional array as mentioned in the comments).

The reason for doing this is for organization and easy look up. If you wanted to see the data stored in the 1st column of the 3rd row it would be as easy as doing _gird[2][0].

Now as to why a 3rd dimension is made as in _grid[i][j] = new Array(); that is specific to what kind of data needs to be stored at that row and column.

Upvotes: 1

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