Subsref question using braces '{}' type and a char subs

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Alexander
Alexander 2011-2-25
Hello, I am implementing subsref in my class for dealing with braces, '{}'. I want to be able to call
>> classname{'chars'}
but all I get is an error:
??? Error using ==> subsref
Too many output arguments.
The debugger never even gets into the subsref function for me to see whats happening. If I use the same logic but for '()' type indexing, it works fine. Similarly, if I use '{}' but with a number I can get the code to to into the subsref, but I need to be able to use '{}' with char subs not a number/index.
Here is the switch case for the '{}' type
switch s(1).type
case '{}'
v = obj.variable(s(1).subs);
if length(s) == 2
B = v.data(s(2).subs);
elseif length(s) == 3
switch s(3).subs
case data
B = v.data(s(2).subs);
case grid
B = v.grid(s(2).subs);
end
else
B = v;
end
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Walter Roberson
Walter Roberson 2011-2-28
I am hypothesizing that for some reason the type is not matching '{}'
Perhaps I have misunderstood. Are you indicating that you have demonstrated that it never reaches the switch s(1).type code? Or is it possible that that switch is executed but '{}' is not what is in s(1).type ?
Alexander
Alexander 2011-2-28
It never reaches the switch s(1).type code. In fact it gives the error above without entering subsref at all. If I put the command into profiler, I don't get any profiling results, just the error.

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采纳的回答

Philip Borghesani
Your class needs a NUMEL function. A string is a matrix in MATLAB so classname{'foo'} is the same as calling classname{double('foo')}. Adding this function to your class will show you what is going on:
function num=numel(obj,varargin)
fprintf('NUMEL called with %d indices',nargin-1);
num=builtin('numel',obj,varargin{:});
fprintf(' NUMEL returned %d\n',num);
end
To make string inputs work the way you want have NUMEL return 1 or prod(size(obj)) for char type inputs depending on what behavior is desired.

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