如何从锯齿状数组以更简化的方式返回数据？

Question

I've created a factory class which allows the user to call a method Generate and it populates a jagged array via some logic that generally I don't want the user to deal with.

A lot of index's are null because of the type of grid layout that the factory generates.

But I don't want the user to have to iterate both array indexes and check for null. Is there anyway to simplify this for a user to iterate this array without them needing to worry about it.

For example, to iterate the data they currently have to do:

for (int i = Map.MapData.Length - 1; i >= 0; --i)
{
    for (int j = Map.MapData[i].Length - 1; j >= 0; --j)
    {
         // would rather they didn't have to check for null
         if (Map.MapData[i][j] == null) continue;

         // do stuff with data
    }
}

This isn't all that user friendly. Is there a way I can make the data be more linear to the user, like using a for each on the data? I'm not entirely sure what I am looking for in order to achieve this, hope some one can point me in the right direction.

Thanks

Answer 1

When querying collections (in your case you want all not null items) try using Linq :

  var NotNullItems = Map
    .SelectMany(line => line      // From each line
       .Where(x => x != null));   // Filter out all null items

  foreach (var item in NotNullItems) {
    // do stuff with data
  }

Answer 2

If you just want to loop through the elements of the array and discard the indices, you can do an extension method:

public static class JaggedArrayExtensions {
    public static IEnumerable<T> IterateNonNull<T>(this T[][] array) where T : class {
        for (int i = array.Length - 1; i >= 0; --i)
        {
            for (int j = array[i].Length - 1; j >= 0; --j)
            {
                // would rather they didn't have to check for null
                if (array[i][j] == null) continue;

                yield return array[i][j];
            }
        }
    }
}

Now you can loop through your jagged array with a foreach loop:

foreach (var item in jaggedArray.IterateNonNull()) {
    // ...
}

If this is the first you see yield return , read this .