It can be useful for a subclass to restrict the range of values of a superclass property to a subset of possibilities allowed by the superclass. Overloading the set. method to accomplish this would be useful for a number of reasons. Furthermore, this restriction of the language provides no guarantee that the superclass invariants will be preserved by the subclass. It only slightly limits the notation that the programmer can use to violate those invariants. A class tree designer who doesn't understand this is going to generate a train wreck in any case.
Training videos and edit-time warnings would be a better option as long as the warnings can be turned off. For example, I don't see how to turn off the warnings I get about the possibility that the final state of an object might be dependent on the sequence in which the properties are set. Since you must not disallow many-to-many relationships between properties of classes there will be classes for which the property setting sequence matters so leave the programmer alone about it and stop coloring up his code if he already knows this.
"Peter" wrote in message <gp55at$jev$1@fred.mathworks.com>...
> > "Peter " <peter.korteweg@apginvestments.nl> wrote
> > Is it possible to overload a property set function?
> >
> <text removed>
>
> > "Steven Lord" <slord@mathworks.com> wrote in message
> > Choose a different property name.
> >
> > An HGroup object isa HMatrix object as well, because the HGroup class
> > inherits from the HMatrix class. Since HMatrix has a datamat property,
> > HGroup inherits that property. Also, an instance of HGroup should be valid
> > anywhere a HMatrix object is (since it isa HMatrix.)
> >
> > Now if you could overload the property set method in the HGroup class, you
> > could have the overloaded method "approve" a value for the datamat property
> > that the HMatrix property set method would not approve. That would mean
> > that the HGroup object with that value would not be a valid HMatrix object
> > and as such potentially would not work in place of a HMatrix object. To
> > prevent that, you can only set a property set method in the class where you
> > actually define the property, and for this example that means the HMatrix
> > class.
> >
> > --
> > Steve Lord
> > slord@mathworks.com
> >
>
> Thanks for the explanation. This makes sense. Although one of my motivations for the code was to add some extra data checks, and then call the inherited set property. From your and Per's comment this seems not possible.
Training videos and edit-time warnings would be a better option as long as the warnings can be turned off. For example, I don't see how to turn off the warnings I get about the possibility that the final state of an object might be dependent on the sequence in which the properties are set. Since you must not disallow many-to-many relationships between properties of classes there will be classes for which the property setting sequence matters so leave the programmer alone about it and stop coloring up his code if he already knows this.
"Peter" wrote in message <gp55at$jev$1@fred.mathworks.com>...
> > "Peter " <peter.korteweg@apginvestments.nl> wrote
> > Is it possible to overload a property set function?
> >
> <text removed>
>
> > "Steven Lord" <slord@mathworks.com> wrote in message
> > Choose a different property name.
> >
> > An HGroup object isa HMatrix object as well, because the HGroup class
> > inherits from the HMatrix class. Since HMatrix has a datamat property,
> > HGroup inherits that property. Also, an instance of HGroup should be valid
> > anywhere a HMatrix object is (since it isa HMatrix.)
> >
> > Now if you could overload the property set method in the HGroup class, you
> > could have the overloaded method "approve" a value for the datamat property
> > that the HMatrix property set method would not approve. That would mean
> > that the HGroup object with that value would not be a valid HMatrix object
> > and as such potentially would not work in place of a HMatrix object. To
> > prevent that, you can only set a property set method in the class where you
> > actually define the property, and for this example that means the HMatrix
> > class.
> >
> > --
> > Steve Lord
> > slord@mathworks.com
> >
>
> Thanks for the explanation. This makes sense. Although one of my motivations for the code was to add some extra data checks, and then call the inherited set property. From your and Per's comment this seems not possible.