Matlab：按属性建立对象数组索引

Question

In Matlab, I would like to create an array of objects from where I can pick up an element by one of its unique property while keeping the same behavior as normal indexing.

Here is the class:

classdef myClass < dynamicprops

    properties
        Name = '';
        Values
    end

    methods
        function obj = myClass(name,values)
            if nargin > 0
                obj.Name = name;
                obj.Values = values;
            end
        end
    end
end

Lets consider the following array :

>> a(1) = myClass('one'  ,[1:10]);
>> a(2) = myClass('two'  ,[2:20]);
>> a(3) = myClass('three',[3:30]);

The easiest way to directly acess to the values of an element is :

>> a(1).Values
ans =
 1     2     3     4     5     6     7     8     9    10

But I would like to call the elements of the array by their name not their index, while keeping the ability to have a direct access to the values :

>> % /!\ This is intended behavior, not real result
>> a('two').Values(end-2:end) * 3
ans =
    54    57    60

I could une two = findobj(a,'Name','two'); two.Values(end-2:end) * 3 two = findobj(a,'Name','two'); two.Values(end-2:end) * 3 but it's not as convinient.

I've tried setting a custom subsref method to my object and it works quite well but I lose some indexing features.

I got the intended behavior with the following method :

function out = subsref(obj,S)
    if strcmpi(S(1).type,'()') && ischar(S(1).subs{1})
        found = findobj(obj,'Name',S(1).subs{1});
        if ~numel(found)
            error(['Object with Name ''' S(1).subs{1} ''' not found.'])
        end
        if numel(S) == 1
            out = found(1);
        else
            out = builtin('subsref',found(1),S(2:end));
        end
    else
        out = builtin('subsref',obj,S);
    end
end

But I can't get all the names/values with [a.Values] or {a.Name} . Matlab returns :

Error using myClass/subsref
Too many output arguments.

And I might lose other indexing features as well.

Is there a better solution for my problem ? Any help would be appreciated.

Answer 1

You can use a varargout in subsref to support getting a list of all the values of the property Values :

function varargout = subsref(obj,S)
    if strcmpi(S(1).type,'()') && ischar(S(1).subs{1}) && ...
        ~strcmp(S(1).subs{1},':')
        found = findobj(obj,'Name',S(1).subs{1});
        if ~numel(found)
            error(['Object with Name ''' S(1).subs{1} ''' not found.'])
        end
        if numel(S) == 1
            varargout{1} = found(1);
        else
            varargout{1} = builtin('subsref',found(1),S(2:end));
        end
    else
        [varargout{1:nargout}] = builtin('subsref',obj,S);
    end
end

Note that I also added ~strcmp(S(1).subs{1},':') to the condition in the first if to support a(:) indexing.

One other consideration I see is how to handle multiple strings:

a('one','two');

or mixed types:

a('one',3:end);

These are more corner cases, but something to consider.