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I'm relatively new to IDL, so I'm sure what I want to do is actually quite trivial!

I'm creating a class with a few member variables. Two of these will just be floats, but the third I would like to be an 3-dimensional array with unknown size (well.. actually I know the size of the third dimension to be 12, but that's it!). How do I declare this in the class definition or is it not possible? Maybe I need to work with a non-array data structure..?

Here's my code so far:

pro field__define
  void={field, lat_res: 0.0, long_res: 0.0, values: ?!?!?!?!}
  return
end
Paul Hiemstra
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tiswas
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2 Answers2

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You want to use a pointer, like:

pro field__define
  void = { field, lat_res: 0.0, long_res: 0.0, values: ptr_new() }
end

By the way, there is no need for a RETURN in the definition, execution returns when it hits an END statement.

This does not actually create a pointer, it just saves space for the pointer. When you want to use the field, you will need to do something like:

self.values = ptr_new(fltarr(3, 4, 5))

Then use the values like:

help, *self.values

Lastly then don't forget to clean up the heap when you are done with array with:

ptr_free, self.values

It might be good to get a book for topics like this, there are a lot of details that following a few examples through can help with.

mgalloy
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An alternate technique that uses a hash to represent the member variables of a class is outlined here. It has an advantage in that it's arguably easier to work with hashes than with pointers in IDL, but it requires at least IDL version 8 to run.

Mark Piper
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