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Topic: Determining 'classname' such that isa(v,'classname') will be true
Replies: 5   Last Post: Apr 22, 2013 11:33 AM

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 Steven Lord Posts: 18,038 Registered: 12/7/04
Re: Determining 'classname' such that isa(v,'classname') will be true
Posted: Apr 17, 2013 10:11 AM

"Paul " <paulremovethispartjackson@jhuapl.edu> wrote in message
news:kkki9r\$s7c\$1@newscl01ah.mathworks.com...
> Given an object v of a class, how can I determine all possible classname
> such that isa(v,'classname') will return true? For example, consider the
> following:
>
> h=ss(1,1,1,1);
> class(h)
> mc=metaclass(h);
> mc.SuperclassList.Name
> L1=isa(h,'ss'); % returns true, understandable
> L2=isa(h,'numlti'); % returns true, understandable
> L3=isa(h,'StateSpaceModel'); % returns true, understandable
> L4=isa(h,'lti'); % returns true, how would I have known?
> [L1 L2 L3 L4]
>
> ans =
> ss

This comes from class(h)

> ans =
> numlti
>
> ans =
> StateSpaceModel

These two come from the _comma-separated list_ mc.SuperclassList.Name.

> ans =
>
> 1 1 1 1
>
> I just stumbled on 'lti' returning true for this case. How could I have
> found that programatically?

Note that while mc is a scalar meta.class object, mc.SuperclassList is a
vector of meta.class objects. ss directly inherits from numlti and
StateSpaceModel. But if you look at the SuperclassList for each of the
elements of the mc.SuperclassList vector of objects, you'll see that numlti
inherits from lti while StateSpaceModel also inherits from another class.
You can walk your way up the inheritance tree using the meta class objects
and their SuperclassList properties until all the meta class objects you
reach have empty SuperclassList properties.

> In general, is there some function that has a functionality like:
> c = whatis(v); % returns cell array c such that isa(v,c{i}) is true

Not directly, but you could write one to walk the whole tree. It wouldn't be
that difficult.

Are you planning to do something tricky and/or clever with this information?
Or is it more something that made you curious?

--
Steve Lord
slord@mathworks.com
http://www.mathworks.com

Date Subject Author
4/16/13 Paul
4/17/13 Steven Lord
4/17/13 Paul
4/18/13 Steven Lord
4/20/13 Paul
4/22/13 Steven Lord