如何在MATLAB方法中清除持久变量 [英] How to clear a persistent variable in a MATLAB method

问题描述

我有一个MATLAB类，其中包含采用持久变量的方法.当满足某些条件时，我需要清除持久变量而不清除该方法所属的对象.我已经能够做到这一点，但是只能通过使用clear functions来实现我的目的.

此问题的classdef .m文件:

classdef testMe

    properties
        keepMe
    end

    methods
        function obj = hasPersistent(obj)
            persistent foo

            if isempty(foo)
                foo = 1;
                disp(['set foo: ' num2str(foo)]);
                return
            end
            foo = foo + 1;
            disp(['increment foo: ' num2str(foo)]);

        end

        function obj = resetFoo(obj)
            %%%%%%%%%%%%%%%%%%%%%%%%%
            % this is unacceptably broad
            clear functions
            %%%%%%%%%%%%%%%%%%%%%%%%%
            obj = obj.hasPersistent;
        end
    end

end

使用此类的脚本:

test = testMe();
test.keepMe = 'Don''t clear me bro';

test = test.hasPersistent;
test = test.hasPersistent;
test = test.hasPersistent;

%% Need to clear the persistent variable foo without clearing test.keepMe

test = test.resetFoo;

%%
test = test.hasPersistent;
test

输出为:

>> testFooClear
set foo: 1
increment foo: 2
increment foo: 3
increment foo: 4
set foo: 1

test = 

  testMe

  Properties:
    keepMe: 'Don't clear me bro'

  Methods

这是所需的输出.问题是classdef文件中的行clear functions清除了内存中的所有功能.我需要一种清除范围较小的方法.例如，如果hasPersistent' was a function instead of a method, the appropriately scoped clear statement would be clear hasPersistent`.

我知道clear obj.hasPersistent和clear testMe.hasPersistent都无法清除持久变量. clear obj同样是个坏主意.

解决方案

在评论中进行讨论之后，我认为您想将make foo用作私有属性，并附带适当的increment/reset公共功能

I have a MATLAB class that contains a method that employs a persistent variable. When certain conditions are met I need to clear the persistent variable without clearing the object to which the method belongs. I've been able to do this, but only by employing clear functions which has excessively broad scope for my purposes.

The classdef .m file for this problem:

classdef testMe

    properties
        keepMe
    end

    methods
        function obj = hasPersistent(obj)
            persistent foo

            if isempty(foo)
                foo = 1;
                disp(['set foo: ' num2str(foo)]);
                return
            end
            foo = foo + 1;
            disp(['increment foo: ' num2str(foo)]);

        end

        function obj = resetFoo(obj)
            %%%%%%%%%%%%%%%%%%%%%%%%%
            % this is unacceptably broad
            clear functions
            %%%%%%%%%%%%%%%%%%%%%%%%%
            obj = obj.hasPersistent;
        end
    end

end

A script that employs this class:

test = testMe();
test.keepMe = 'Don''t clear me bro';

test = test.hasPersistent;
test = test.hasPersistent;
test = test.hasPersistent;

%% Need to clear the persistent variable foo without clearing test.keepMe

test = test.resetFoo;

%%
test = test.hasPersistent;
test

The output from this is:

>> testFooClear
set foo: 1
increment foo: 2
increment foo: 3
increment foo: 4
set foo: 1

test = 

  testMe

  Properties:
    keepMe: 'Don't clear me bro'

  Methods

which is the desired output. The problem is that the line clear functions in the classdef file clears all functions in memory. I need a way to clear with a much smaller scope. For example, if hasPersistent' was a function instead of a method, the appropriately scoped clear statement would beclear hasPersistent`.

I know that clear obj.hasPersistent and clear testMe.hasPersistent both fail to clear the persistent variable. clear obj is similarly a bad idea.

解决方案

Following the discussion in the comments, I think you want to use make foo a private property, accompanied with appropriate increment/reset public functions.

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