callback within the class?

hi, i got the following class:

 classdef form<handle
          properties
              type = 'square'
              b
              h
              A
              Iy
              Iz
              Wy
              Wz
          end %properties
          events
              calc
          end %events
          methods
              function f = form(b,h)
                  f.b=b;
                  f.h=h;
                  f.update()
              end 
              function obj = update(obj)
                  obj.A= obj.h*obj.b;
                  obj.Iy= obj.h^3*obj.b/12;
                  obj.Iz= obj.b^3*obj.h/12;
                  obj.Wy= obj.h^2*obj.b/6;
                  obj.Wz= obj.b^2*obj.h/6;
              end
          end % events
      end%class

how do i manage to call the function update everytime when either form.a or form.h of an instance is changed withoud adding a listener to the instance? is there a way to directly built thin in the class definition?

thanks a lot for help

Answer 1

[Daniel Shub]

It seems like all the properties other than b and h should be dependent. This would allow you to get rid of the update method. If you really want to go the update route, you could write a set method for b and h which will call the update method.

Does the following work for you?

classdef form<handle
  properties
    type = 'square'
    b
    h
  end
  properties (Dependent)
    A
    Iy
    Iz
    Wy
    Wz
  end %properties
  methods
    function f = form(b,h)
      f.b=b;
      f.h=h;
    end
    
    function val = get.A(obj)
      val= obj.h*obj.b;
    end
    
    function val = get.Iy(obj)
      val= obj.h^3*obj.b/12;
    end
    
    function val = get.Iz(obj)
      val= obj.b^3*obj.h/12;
    end
    
    function val = get.Wy(obj)
      val= obj.h^2*obj.b/6;
    end
    
    function val = get.Wz(obj)
      val = obj.b^2*obj.h/6;
    end
  end % events
end%class

You could also go with the "ugly" update method:

classdef form<handle
  properties
    type = 'square'
    b
    h
    A
    Iy
    Iz
    Wy
    Wz
  end %properties
  methods
    function f = form(b,h)
      f.b=b;
      f.h=h;
    end
    function set.b(obj, val)
      obj.b = val;
      obj.update;
    end
    function set.h(obj, val)
      obj.h = val;
      obj.update;
    end
    function obj = update(obj)
      obj.A= obj.h*obj.b;
      obj.Iy= obj.h^3*obj.b/12;
      obj.Iz= obj.b^3*obj.h/12;
      obj.Wy= obj.h^2*obj.b/6;
      obj.Wz= obj.b^2*obj.h/6;
    end
  end % events
end%class

Answer 2

[Walter Roberson]

You do not appear to have a form.a . You do have a form.A which is overwritten in update() . If update() is to be called as a callback when form.A is changed, then it would be called when form.A is changed within update()

What is the point of having an update when form.A is changed, if the value of form.A is going to be ignored?

Is it perhaps form.b you wish to trigger update() on?

[jeff wu]

yes sorry, when form.h and form.b are changed the update shall be lunshed again