Overloading end indexing for user defined classes

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Leon 2022-2-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1654935-overloading-end-indexing-for-user-defined-classes

回答： Leon 2022-2-22

When overloading parenthesis indexing for user defined classes, is there a way to overload 'end' indexing such that it behaves differently for '()' and '{}' indexing. For example, I would like that 'myClass(end)' returns the last object in the object array, whereas 'myClass{end}' returns the last element of a property defined in myClass. The solution should also be valid for slicing, e.g. 'myClass(100:end)'.

Could this be implemented in the overloaded 'subsref()' method or possibly in the overloaded 'end()' method?

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Rik 2022-2-21

I would assume you can leave end alone and only overload subsref. Did you try anything yet?

Leon 2022-2-21

在 MATLAB Online 中打开

Yes, I overloaded end method to act on object property, but this ruined object array behaviour:

function out = end(obj, k, ~)
     % Overload object indexing with 'end()'
     out = size(obj.trcArr, k);
end

And the shortened version of overloaded indexing method:

function varargout = subsref(obj, s)
    % Overload parenthesis indexing.
    % Structure 's' defines indexing where only '{}' is changed.
    % Indexing using '()' and '.' is kept as default.
    switch s(1).type
        case '.'
            % Keep built-in functionality for '.'
            [varargout{1:nargout}] = builtin('subsref', obj, s);
        case '()'
            % Keep built-in functionality for '()'
            [varargout{1:nargout}] = builtin('subsref', obj, s);
        case '{}'
            % Implement obj{index} functionality
            % My code is here
            % Could I call different 'end()' implementation for '{}' indexing from here
        otherwise
            error('Indexing expression invalid.')
    end
end

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Answer 1

Leon 2022-2-22

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1654935-overloading-end-indexing-for-user-defined-classes#answer_901895

I have manged to resolve this by omitting subsref() method and inheriting the new indexing class 'matlab.mixin.indexing.RedefinesBrace' that was introduced in 2021b. This one gives you more control over indexing and is easier to implement.

https://uk.mathworks.com/help/matlab/ref/matlab.mixin.indexing.redefinesbrace-class.html