MATLAB: Does DocExtendDouble example produce an error while using subscripted assignment

Question

I am trying the example on the documentation page for "Example — Adding Properties to a Built-In Subclass" found by typing the following at the MATLAB Command Prompt:

 web([docroot '/techdoc/matlab_oop/brgze9_-1.html#brrpjb7'])

Or by navigating to the following URL:

 <http://www.mathworks.com/access/helpdesk/help/techdoc/matlab_oop/brgze9_-1.html#brrpjb7>

I have made the class definition file for DocExtendDouble.

When I execute the following commands:

ed = DocExtendDouble(1:10,'One to ten');
ed(1:5) = 5:-1:1

I get the following error:

 ??? Input argument "str" is undefined.
 Error in ==> DocExtendDouble>DocExtendDouble.DocExtendDouble at 14
          obj.DataString = str;

Answer 1

This change has been incorporated into the documentation in Release 2009a (R2009a). For previous releases, read below for any additional information:

This behavior is a bug in the class definition file provided in the documentation for "Example — Adding Properties to a Built-In Subclass". When the command

ed(1:5) = 5:-1:1

is executed, the constructor for the DocExtendDouble class gets called. The constructor does not find the expected second argument called "str" of type string, and thus produces the error.

As a workaround, replace the constructor for the DocExtendDouble class definition with the following:

function obj = DocExtendDouble(data,str)
      if nargin == 0
          data = [];
      elseif nargin < 2
          str = '';
      end
      obj = obj@double(data);
      obj.DataString = str;         
end