Property validation against another property

Hello, I am using matlab system object in Simulink and set two of its properties via mask. I want to make sure that the value of property two (max_cmd) is greater than the value of property one (min_cmd):

properties(Access = public)

% min_cmd Minimum command

min_cmd (1,1){mustBeNonnegative} = 0

% max_cmd Maximum command

max_cmd (1,1){mustBeNonnegative, mustBeGreaterThan(max_cmd, min_cmd)} = 1000000

end

Unfortunately, I get the following error:

Validator arguments must be either 'max_cmd' or constant literal values.

Any ideas how to validate max_cmd > min_cmd? Thank you!

[chrisw23]

have you tried ?

max_cmd (1,1){mustBeNonnegative, mustBeGreaterThan(max_cmd, obj.min_cmd)} = 1000000

Answer 1

[David Szwer]

I don't think this is possible using a validation function. The help page says, "Additional arguments must be literal values and cannot reference variables. Literal values are nonsymbolic representations, such as numbers and text."

To do what you want, you could write a set method (enforcing the condition), and an explicit constructor for the object (also enforcing the condition). For example:

methods

function obj = set.max_cmd(obj,value)

if (value > obj.min_cmd)

obj.max_cmd = value;

else

error('Max command must be greater than min command.')

end

end

end

However, this will give you a warning that get/set methods should not access other properties. You may be able to ignore this warning if you are very careful; see:

https://uk.mathworks.com/matlabcentral/answers/455757-access-different-property-from-set-method-in-class

https://uk.mathworks.com/help/matlab/matlab_oop/avoiding-property-initialization-order-dependency.html

Probably your best bet is to make those properties private, without validation, and create public methods like setLowerLimit(obj, min_cmd) that can enforce the conditions using both properties.

[Giacomo Riva]

"Probably your best bet is to make those properties private, without validation, and create public methods like setLowerLimit(obj, min_cmd) that can enforce the conditions using both properties."

If we set the properties to private, then no access for getter or setter methods will be granted. But your approach seems to work if the properties are public and not initialised by the constructor.

In fact, I think it's even a use-case example of setter methods from the Matlab documentation:

Property Get and Set Methods - MATLAB & Simulink - MathWorks United Kingdom