Why do I get the error "Invalid default value for property" when trying to define one default instance variable value in terms of another?

Why do I get the error "Invalid default value for property" when trying to define one default instance variable value in terms of another?

e.g.

classdef Example
    properties
        A = {'a','b','c'}
        B = [A,'d']
    end
end

gives me the following error when I try to instantiate an example object

>> Example

Invalid default value for property 'B' in class 'Example':

Undefined function or variable 'A'.

Answer 1

[MathWorks Support Team]

It is easier to see the reason for this issue once you fully-qualify the name of an instance variable with which you are defining another.

e.g.

classdef Example
    properties
        A = {'a','b','c'}
        B = [Example.A,'d']
    end
end

yields the error

>> Example

Invalid default value for property 'B' in class 'Example':

The property 'A' in class 'Example' must be accessed from a class instance because it is not a Constant property.

Because 'B' is defined in terms of A, we must either define 'A' to be a "Constant" property or we must initialize B in the constructor.

i.e.

classdef Example
    properties (Constant)
        A = {'a','b','c'}
    end
    properties
        B = [Example.A,'d']
    end
end

or

classdef Example
    properties
        A = {'a','b','c'}
        B
    end
    methods
        function obj = Example()
            obj.B = [obj.A,'d'];
        end
    end
end