Clean way of writing a setter that can set nested private properties

Is there a clean way to write a setter for private properties/members that can accept nested properties?

Something with an API like:

function set(obj, property, value)

that can be called like:

obj.set('property_name.subproperty_name', value)

I can think of an easy but verbose way:

props = split(char(property), '.')
if numel(props) == 1
    if obj.(props{1}) == value, return; end
    obj.(props{1}) = value;
    ...
else if numel(props) == 2
    ...
end

or a way using setfield (but then all properties need to be public):

props = split(char(property), '.')
if getfield(obj, props{:}) == value, return; end
obj = setfield(obj, props{:}, value);
...

I am asking in case anyone knows a solution to this.

I want to have this in a custom setter because it checks if the variable has changed and it updates stuff if it has.

Thanks!

[Matt J]

obj.set('property_name.subproperty_name', value)

Which property in the chain is supposed to be private, here? Do we assume subproperty_name is private to property_name? It shouldn't matter if property_name is private to class(obj). The set() method of class(obj) can access its private properties.

[ErikJ GiesenLoo]

Assume property_name is private. The set method can access private members, but implementation wise if I use getfield/setfield I cannot set 'property_name.subproperty_name' unless they are public. Conversely, I can try to assign obj.('property_name').('subproperty_name') but I'd have to check if props is split into 1, 2 or more nested properties (which is not clean imo).

I thought about using eval("obj" + property = value) but everyone says eval is evil, so I assume there is a better way.

Edit: I was looking thru the history of your comments and I think there is possibly a recursive way of writing it

Edit 2: I wrote a recursive function but it seems to make a copy of obj.(stuff) so it doesnt work

Answer 1

[ErikJ GiesenLoo]

Further responses are welcome this query, but here is one clunky alternative using a helper set_ function that takes in the base object two times (this and obj), a string array props (instead of cell array of chars), and the value to be assigned:

function [obj, update] = set_(this, obj, props, value)
  if numel(props) > 1
    [obj.(props(1)), update] = this.set_(obj.(props(1)), props(2:end), value);
  else
    update = ~isequal(obj.(props(1)), value);
  	obj.(props(1)) = value;
  end
end

This needs to be called by a function set(this, props, value) as described in the question. the variable update tells set that a variable has changed and do further stuff. That further stuff cannot be called direcly at the base case of the helper set_ funciton because obj.(props(1)) needs to be reassigned to the base object.

Edit: changed helper function and now seems to work as expected