Converting multidimensional array elements to different type

Question

Suppose I have this multidimensional array:

float[][,] vertices = { 
            new float[,]{ {0f, 1.28f}, {1.28f, 2.56f}, {3.84f, 2.56f}, {5.12f, 1.28f}, {3.84f, 0f}, {1.28f, 0f}, {0f, 1.28f} }, 
            new float[,]{ {0f, 3.83f}, {1.27f, 5.12f}, {3.87f, 5.12f}, {5.12f, 3.83f}, {5.12f, 1.26f}, {3.87f, 0f}, {1.27f, 0f}, {0f, 1.26f}, {0f, 3.83f} } 
        };

Now, I want to convert each subarray to an array of type Vector2[] where Vector2 is a public class, which simply contains x and y properties:

public class Vector2 {
  public float x;
  public float y;

  public Vector2(float x, float y) { this.x = x; this.y = y }
}

So I want to construct Vector2 elements from Array[2] elements, which are subarrays in above vertices array variable.

I do it like this:

Array.ConvertAll(vertices[0], 
    new Converter<float[], Vector2>(verticesSequence => { return new Vector2(verticesSequence[0], verticesSequence[1]); }));

However, in return I receive this error message:

Error 15 The best overloaded method match for 'System.Array.ConvertAll(float[][], System.Converter)' has some invalid arguments

Answer 1

You have an array, which contains two arrays, each of which contains a different number of float arrays.

Array.ConvertAll is suitable for converting one array into the other by specifying a mapping delegate (one to one). In this case, you don't only have to convert a single float[,] into a Vector2. Note that you also used a float[] to Vector2 converter, instead of float[,] to Vector2.

Multidimensional arrays like float[,] are also a bit tricky since they don't support LINQ out of the box, which it a bit harder to create a one-liner which would do all the mapping.

In other words, you will at least need a helper method to map the items of the multidimensional array:

public static IEnumerable<Vector2> ConvertVectors(float[,] list)
{
    for (int row = 0; row < list.GetLength(0); row++)
    {
        yield return new Vector2(list[row, 0], list[row, 1]);
    }
}

And then you can use that inside the Array.ConvertAll method:

var converted = Array.ConvertAll<float[,], Vector2[]>(
    vertices,
    ff => ConvertVectors(ff).ToArray());

Honestly, I would prefer a LINQ solution because it will infer all the generic parameters automatically:

var r = vertices
    .Select(v => ConvertVectors(v).ToArray())
    .ToArray();