How to programmatically modify substructure with arbitrary number of levels?

I am trying to create a function that can modify a field in an arbitrary deep structure in the following way:

function modified_struct = modify_field(original_struct, field_name_cell_aray, new_value)

For instance if I have an original_struct such that

original_struct.a.b = 1

calling

modified_struct = modify_field(original_struct, {'a', 'b'}, 2)

would create the following operations

modified_struct = original_struct
modified_struct.(a).(b) = 2

This should work for a struct with an arbitrary number of levels:

modified_struct = modify_field(original_struct, {'a', 'b', 'c', 'd'}, new_value)

I want a solution that does not use the eval() command since I need to use this in a parfor loop.

Is this possible in matlab?

Answer 1

[Stephen23]

I would not write a function for this, just use SETFIELD with a comma-separated list:

S.a.b = 1;
C = {'a','b'};
N = 2;
S = setfield(S, C{:}, N);

Checking:

S.a.b

ans = 2

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/1656435-tutorial-comma-separated-lists-and-how-to-use-them

[Simon Fortin-Deschenes]

Amazing tool to add to my toolbox, thank you!

Answer 2

[Jean-Baptiste Lanfrey]

If I understand correctly, all you need is to use the setfield command, for example:

modified_struct = setfield(original_struct, 'a', 'b', 2)

The field arguments are not in a cell array but I guess it is easy enough to accomodate for this.