Defined method can not be invoked.

I want to extend ss object. But, the methods can not de invoked in the file.

Am I using wrong way?

Here is my object

classdef ssSpring < ss
    %SSSPRING Summary of this class goes here
    %   Detailed explanation goes here
    properties (Access = public)
        x0;
    end
    
    methods
        function sys = ssSpring()
            sys.A=[0,0,0,1,0,0;0,0,0,0,1,0;0,0,0,0,0,1;-1,1,0,0,0,0;1,-2,1,0,0,0;0,1,-1,0,0,0];
            sys.B=[0;0;0;1;0;0];
            sys.C=[0,0,1,0,0,0];
            sys.D=[0];
            sys.x0=[0.323811195852370;0.430986087686128;0.764897800510776;0.996462675076854;0.265018285144099;0.792067001328556];
        end
    end
    methods (Access=public)
        function b = printa(a)
            b=a;
        end
    end
end 

[Walter Roberson]

Which method cannot be invoked in what file?

[younghwa park]

Thanks for seeing my quesiton!

sys=ssSpring()
sys.printa(1)

returns errors.

Answer 1

[Walter Roberson]

The first parameter to a non-static non-constructor class method is always the class object that is being operated on. That would be sys in the context of your code. You then attempt to pass a second parameter with value 1 but the method is only defined to accept one parameter.

sys.printa(1)

is the same as

   printa(sys, 1)

[Steven Lord]

The first parameter to a non-static non-constructor class method is always the class object that is being operated on.

That's not always correct. At least one of the inputs to a non-Static and non-constructor class method must be an instance of the class, but it does not necessarily need to be the first input. As an example both of the following calls would use the plus method of the sym class even those in the second case the first input is the double value 1.

syms x
which plus(x,1)

/MATLAB/toolbox/symbolic/symbolic/@sym/plus.m  % sym method

which plus(1,x)

/MATLAB/toolbox/symbolic/symbolic/@sym/plus.m  % sym method

If both the inputs are objects, the rules for which class's method gets called are listed here. When InferiorClasses are involved, the first object is not always the one whose method gets called.

But your point about the method needing to be defined to accept two inputs rather than just one is correct and is the root cause of the error @younghwa park received.

[Walter Roberson]

Good point, @Steven Lord