MATLAB: How to access a field on a struct which is not always in the same level

access fieldsMATLABstruct

Hello,
I have a problem in generalizing a code for different structure contents. The problem is that I need to access a field (let's say subfield1) which is not always in the same level of the structure.
var1.subfield1 = 1;
var2.field1.subfield1 = 3;
I would like to be able to define a variable, fieldname, that would be empty for var1 and 'field1' for var2, so that:
var1.(fieldname).subfield1
var2.(fieldname).subfield1
would work and give me the value of that field. However if I set:
fieldname=''
and try to execute the first line, this gives an error:
Reference to non-existent field ''.
I have also tried using the getfield function, with no success.
Is there any solution for this, or should the structures have the same fields from the beginning to be able to do this?
Thank you very much in advance,
Ana Gómez

Best Answer

Create a function which checks the existence of the subfield:
function Data = getSubField(S, F1, F2)
if isfield(S, F2)
  Data = S.(F2);
elseif isfield(S, F1)
  Data = S.(F1).(F2);
else
  Data = [];
end
Now call this like:
var1.subfield1 = 1;
var2.field1.subfield1 = 3;
Data1 = getSubField(var1, 'field1', 'subfield1');
Data2 = getSubField(var2, 'field1', 'subfield1');
If run-time matters, this might be faster - or slower (try it by your own):
function Data = getSubField(S, F1, F2)
try
  Data = S.(F2);
catch
  try
    Data = S.(F1).(F2);
  catch
    Data = [];
  end
end
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