Problem with properties in App Designer.

Hello. I need help with "properties" in App Designer. I have some trouble with realization the method of symmetrical components.

 properties (Access = public)
     a = -.5 + sqrt (3) / 2 * j; % Phase-shift operator
     F = [1 a^2 a; 1 a a^2; 1 1 1]; % Matrix Fortescue
 end

Message: "Invalid default value for property 'F' in class 'App1': Undefined function or variable 'a'."

If I replace "a" with "app.a" in the Matrix Fortescue.

Message: "Invalid default value for property 'F' in class 'App1': Undefined variable "app" or class "app.a"."

Answer 1

[Steven Lord]

Since you're probably not going to want a and F to change based on the state of your app, make them Constant properties, properties with the Constant attribute.

[New]

 properties (Constant)
     a = 1; 
     b = a+1;
 end

function ButtonPushed(app, event)
    app.EditField.Value = app.EditField.Value + app.b;
end

Message: Invalid default value for property 'b' in class 'App1': Undefined function or variable 'a'.

[Steven Lord]

You want to define the property app.b in terms of the property app.a, not a variable a. In the first example on the documentation page to which I directed you, note how property NamedConst.D is defined in terms of property NamedConst.R and not on a variable named R.

[New]

1 example: Invalid default value for property 'F' in class 'App1': Undefined variable "app" or class "app.a".

properties (Access = public)
    a = -.5 + sqrt (3) / 2 * j; % Phase-shift operator
    F = [1 app.a^2 app.a; 1 app.a app.a^2; 1 1 1]; % Matrix Fortescue
end

2 examle: Just replace 'app.a' with value 'a' in 'F'.

properties (Access = public)
    a = -.5 + sqrt (3) / 2 * j;
    F = [1 (-.5 + sqrt (3) / 2 * j)^2 -.5 + sqrt (3) / 2 * j; 1 -.5 + sqrt (3) / 2 * j (-.5 + sqrt (3) / 2 * j)^2; 1 1 1];
end

3 example: Add startup function.

properties (Access = public)
    a = -.5 + sqrt (3) / 2 * j;
    F;
end
...
function startupFcn(app)
    app.F = [1 app.a^2 app.a; 1 app.a app.a^2; 1 1 1];
end

2 and 3 example work true. But how define property on other properties in the first case? And what difference between 3 and 1 case?

[Steven Lord]

The name of your app class is App1? Then you need App1.a. In general if your app class was named CLASSNAME, you would use CLASSNAME.a.

[New]

No, prefix does not depend on the name of the application or classname.

[Steven Lord]

That is correct IF you're referring to a property of an instance of the class. A Constant property can be accessed even if you don't have an instance of the class, and the way you do that is by using the name of the class.