Setter methods for dynamic properties

Hello,

I have been working with a class that has dynamic properties that I would like to have setter methods for. The problem is that I don't know how many or the names of the dynamic properties, so I want to have just one setter that takes the name of the property as an argument. However this breaks the part of MATLAB that determines whether or not you're in a setter function (so that when you set the variable it just sets the variable, instead of calling the setter recursively). Here's some example code that illustrates what I'm talking about:

classdef myClass < dynamicprops
    methods
        function obj = myClass()
            P = addprop(obj, 'myProp');
            P.SetMethod = @(o,p)SetProp(o,'myProp',p);
        end

          function SetProp(obj, propname, val)
              obj.(propname) = val;
          end
      end
  end

Now if you try:

x = myClass();
x.myProp = 7;

the method SetProp gets called recursively until MATLAB throws an error. Is there another way to go about this that I am missing? Thanks in advance.

-Andrew

[Oleg Komarov]

Are you looking for something like:

x.set('someprop',value)

[Andrew Barton]

Not quite, I'd really like the user of the class to be able to assign the property using normal syntax, i.e:

x.someprop = value

[Jim Hokanson]

See Also:

http://www.mathworks.com/matlabcentral/answers/48831-set-methods-for-dynamic-properties-with-unknown-names

Answer 1

[Daniel Shub]

What about overloading subsasgn

classdef myClass < dynamicprops
    methods
        function obj = myClass()
            P = addprop(obj, 'myProp');
        end
    function A = subsasgn(A, S, B)
      switch S.type
        case '.'
          SetProp(A, S.subs, B);
      end
    end
      
          function SetProp(obj, propname, val)
              obj.(propname) = val;
          end
      end
  end

[Andrew Barton]

Thanks for the idea, that looks like it would fix my problem, but it also seems like it would force me to reimplement normal array indexing for S.type case '()' which I would obviously rather avoid.

I really think there must be a way to pass the name of the property assigned to the SetMethod function, otherwise attaching SetMethods to dynamic properties would be completely useless in all cases.

[Andrew Barton]

Nevermind, I just now stumbled on the 'builtin' funtion. This solution works perfectly.

Answer 2

[Sebastian Hölz]

I believe the best method is to temporarily disable the property set method in the defined setter-method:

classdef myClass < dynamicprops
    
    methods
        function obj = myClass()
            prop_name = 'myProp'
            P = addprop(obj, prop_name);
            
            prop.SetMethod = @(obj, val)SetProp(obj, prop_name, val, P);
        end
        
         function SetProp(obj, prop_name, val, P)
             
             % disable setter-method
             tmp = P.SetMethod;
             P.SetMethod = [];
             
             % Set value, this could include some more error checking ...
             obj.(prop_name) = val;
             
             % Reset setter-method
             P.SetMethod = tmp;
         end
    end
end