MATLAB: How to find all objects with a specific Property in the workspace, in MATLAB R2011a (7.12)

handleinstanceMATLAB

My workspace contains a set of objects of different Classes (all derived from Handle), some of which contain a certain Property. I desire to find the objects which contain that particular Property only.

Best Answer

The following code demonstrates how to accomplish this functionality. Suppose there are two classes defined as follows:

classdef testClassA < dynamicprops
      properties        
          propA        
      end    
end
classdef testClassB < handle  
      properties        
          propB        
      end    
end

With those two classes, use the following script to look up all the objects instantiated from a given class. One needs to specify in the script the name of Class, whose objects will be searched for a particular Property.

A1 = testClassA;
A2 = testClassA;
A3 = testClassB;
% Test Property which will be searched for
propName   = 'newPropA';
A2.addprop(propName);     
% Objects of Class, or Subclass, of 'className' will be found
className  = 'testClassA'; 
wrkSpcVars = who;
isObj      = false(size(wrkSpcVars)); 
for idx = 1:length(wrkSpcVars) 
      isObj(idx) = isa( eval(wrkSpcVars{idx}), className );
end 
% Find the corresponding objects
myObjs   = cellfun( @eval , wrkSpcVars(isObj), 'UniformOutput', false);
% Find objects with desired Property from the above list
hasProp  = cellfun( @(x) ismember( propName, properties(x) ) , myObjs );
% The result is stored in propObjs
propObjs = myObjs(hasProp);

Related Solutions

MATLAB: How to find the names of private dynamic properties in MATLAB 7.8 (R2009a)

The ability to retrieve the names of Private Dynamic properties is not available in MATLAB R2009a.

As the name suggests, dynamic properties are dynamically added so that means that at some point in time (when you actually add the property) the name should be known. Please make sure you do not lose track of the name at that point. A way to ensure this could be to write you own superclass which keeps track of the property names and derive your class from this class instead of from dynamicprops; an example of such a super class is given below:

classdef mydynamicprops < dynamicprops
      properties (Access=private)
          % In this private property we save the names of the dynamically
          % added properties
          dynpropnames
      end
      methods
          function y=addprop(obj,pname)
              % First add the property to the list of dynamic properties
              obj.dynpropnames{end+1} = pname;
              % Then call the addprop method of dynamicprops, which actually adds the dynamic property 
              y=addprop@dynamicprops(obj,pname);
          end
          function y=GetDynamicProperties(obj)
              % Return a list of dynamic properties
              y=obj.dynpropnames;
          end
      end
end

MATLAB: How to write ‘setter’ methods for properties with unknown names

The infinite recursion is caused by the line 'obj.(propname) = val;' in setProp. This calls the SetMethod for the property 'propname'. When setting the value of a property, MATLAB checks to see if you are currently in the SetMethod for that property in order to avoid infinite recursion. However, since your SetMethod is an anonymous function which calls setProp (and not setProp itself), this assignment is not inside the SetMethod, and the assignment calls the anonymous function.

To avoid this issue, you may use a nested function as shown below:

% start of file MyClass2.m
classdef MyClass2 < dynamicprops
    methods
        function obj = MyClass2(propname, val)
            P = obj.addprop(propname);
            P.SetMethod = propSetFcn(obj, propname);
            obj.(propname) = val;
        end
    end
end
function f = propSetFcn(obj, propname)
    function setProp(obj, val)
        % do other stuff
        obj.(propname) = val;
    end
f = @setProp;
end
% end of file MyClass2.m

Best Answer

Related Solutions

MATLAB: How to find the names of private dynamic properties in MATLAB 7.8 (R2009a)

MATLAB: How to write ‘setter’ methods for properties with unknown names

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