MATLAB: Can I find out if a class is an abstract class before trying to instantiate it

abstract class

Can i somehow say:

if isAbstract(className)

   % do something

else

% do something else

end

Best Answer

A class is abstract if any of its properties or methods is abstract.

It's possible to write a function, is_abstract. Start:

    mco = ?my_class
    mco.PropertyList
    mco.MethodList
    any([mco.MethodList.Abstract])

or better

    mcls = meta.class.fromName('ClassName')

Related Solutions

MATLAB: How to override inherited methods

You can't do what you asked. If you could, you could relax the property setting validation to the point where your subClass instance wouldn't be a valid superClass instance.

You may be able to do what you want, however. Your superClass's property setter could call a normal instance method that subClass could overload. See the trustedSubclassSetterHelper methods in the attached superClass495080 and subClass495080. That helper doesn't actually set the property (otherwise you get into a loop) but merely provides the updated value. This means that the value would have to be something both superClass495080 (in set.prop1) and subClass495080 (in trustedSubclassSetterHelper) accept as a valid value.

>> Q = superClass495080
Q = 
  superClass495080 with properties:
    prop1: 'Hello!'
    prop2: 'My name is'
>> Q2 = subClass495080
Q2 = 
  subClass495080 with properties:
    prop3: 'Dom.'
    prop1: 'Hello World!'
    prop2: 'My name is'

MATLAB: Modifying an immutable/protected variable of a subclass in a superclass method

You're trying to break the fundamental model of OOP: encapsulation. The whole concept of protected properties is that only the class (or its subclasses) can modify them. A superclass has no way to modify the properties of its subclasses. For that matter, there's no guarantee that a subclass would have the propery that it's trying to modify.

Secondly, why are you trying this indirect method for setting properties? Can't you just set the properties of the subclass the normal way? Or even just override your setProperties method in the subclass?

If you really want to set the properties from the superclass, what you can do though is have a method setsubProperties in the superclass that you then override in the subclass. You dispatch to this method from the setProperties method:

classdef Sup < handle %has to be a handle class to modify its own properties
    methods
       function setProperties(this, varargin)
           this.setsubProperties(varargin);
       end
   end 
     methods (Access = protected)
         function setsubProperties(this, varargin)
              error('function must be overriden');
         end
     end
  end
classdef sub < Sup
    methods (Access = proteced)
       function setsubProperties(this, varargin)
           for varg = 1:2:numel(varargin)
               %...
           end
       end
    end
 end

Best Answer

Related Solutions

MATLAB: How to override inherited methods

MATLAB: Modifying an immutable/protected variable of a subclass in a superclass method

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