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From: Steven Lord on 23 Apr 2010 10:08

"sravan kumar" <fourthbatch.cse(a)gmail.com> wrote in message
news:hqrjsh$k4o$1(a)fred.mathworks.com...
> wat is meant by
> "constructor must preserve the class of the returned object".

If you're writing the constructor for your class, let's say the book class,
then whatever it returns must be an instance of the book class itself. You
can't do something like:

classdef book
properties
% some properties here
end
methods
function obj = book(genre, varargin)
if nargin < 1
genre = '';
end
switch genre
case 'comic'
obj = createComicInstead(varargin);
case 'textbook'
obj = createTextbookInstead(varargin);
otherwise
% etc
end
end
end
end

and have book's constructor sometimes return a comic object and sometimes a
textbook object, even if both those classes are subclasses of book.

--
Steve Lord
slord(a)mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ


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