Resolve Error: Nontunable Property Cannot Be Defined by Subscripted Assignment

Issue

If a nontunable property of a System object™ is a structure, you must completely assign the structure when you define it. If you use subscripting to perform partial assignment of a structure in a System object property, you see this error during code generation:

The nontunable property 'myProperty' of class 'MySystemObject' cannot be defined by subscripted assignment. Use complete assignment instead.

Possible Solutions

Consider the System object MySystemObject, which has a single nontunable property. The function useMyObj_error uses the System object. The function creates an instance of MySystemObject. It implicitly defines nonTunableProperty as a structure by assigning values to nonTunableProperty.fieldA and nonTunableProperty.fieldB. Because the function defines nonTunableProperty as a structure and it does not assign values to all fields of the structure simultaneously, code generation fails for useMyObj_error.

classdef MySystemObject < matlab.System
    properties(Nontunable)
        nonTunableProperty
    end

    methods(Access = protected)
        function stepImpl(obj)
            disp(obj.nonTunableProperty);
        end
    end
end

function useMyObj_error
mySystemObject = MySystemObject;
mySystemObject.nonTunableProperty.fieldA = "a";
mySystemObject.nonTunableProperty.fieldB = "b";
mySystemObject(); 
end

To resolve this error, assign values to all fields of the structure when you define it. For example, code generation succeeds for this function.

function useMyObj
mySystemObject = MySystemObject;
mySystemObject.nonTunableProperty = struct("fieldA","a","fieldB","b");
mySystemObject(); 
end