Why can't we define destructors for non-handle classes?

Question

Matthew Fall 2022-12-13

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1877622-why-can-t-we-define-destructors-for-non-handle-classes

回答： Matthew Fall 2022-12-13

I looked up documentation for destructors in Matlab, but it seems like they can only be defined for handle classes. Why is that? I can easily think of a use case for a non-handle class that needs a destructor:

classdef FileReader
    % FileReader very simple file reader
    properties
        fid
    end
    methods
        function obj = FileReader(file)
            obj.fid = fopen(file, 'r');
        end
        function varargout = read(obj,varargin)
            [varargout{1:nargout}] = obj.fread(obj.fid, varargin{:});
        end
        function delete(obj)
            fclose(obj.fid);
        end
    end
end

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Answer 1

Matthew Fall 2022-12-13

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1877622-why-can-t-we-define-destructors-for-non-handle-classes#answer_1127382

在 MATLAB Online 中打开

Never mind, I figured out how to do this with onCleanup:

classdef FileReader
    % FileReader very simple file reader
    properties
        fid
    end
    properties(Access=protected)
        cleanup
    end
    methods
        function obj = FileReader(file)
            obj.fid = fopen(file, 'r');
            obj.cleanup = onCleanup(@() obj.delete);
        end
        function varargout = read(obj,varargin)
            [varargout{1:nargout}] = fread(obj.fid, varargin{:});
        end
        function delete(obj)
            fclose(obj.fid);
            disp('file closed!')
        end
    end
end