constructor called twice when creating array of object. why?

This is sort of a double post, as it is an issue I ran into when following a solution to a previous problem. So, sorry for that, but this really confuses me. As an example, I have a class

 classdef someClass
  properties
      name
      value
  end
  methods
      function obj = someClass(name)
          if ~nargin
              % the default constructor. Needed for array creation
              obj.name = '';
          else
              % only take care of the array part for simplicity:
              if iscell(name)
                  [obj(1:length(name)).name] = deal(name{:});
              end
          end          
          display('object created')
      end
  end
end

When I run c=someClass({'a' 'b' 'c' 'd' 'e'}) I get the output object created object created

c =

1x5 someClass

Properties:
  name
  value

Methods

So, the constructor seems to be called twice. The second time, it is called w/o input arguments. So if I comment the blocks that checks for number of input arguments to be >0, I get the result Error using someClass (line 13) Not enough input arguments.

Error in someClass (line 14) [obj(1:length(name)).name] = deal(name{:});

when I run c=someClass({'a' 'b' 'c' 'd' 'e'}). Why does it run the constructor twice? How can I avoid that.

Thanks for any help, Chris

Answer 1

[Daniel Shub]

The documentation says that "During the creation of object arrays, MATLAB might need to call the class constructor with no arguments ..." While you might be able to avoid it, I don't think it is a good idea.