SIngleton implementation without persistent variables

Question

Rohan 2024-8-28

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2148354-singleton-implementation-without-persistent-variables

评论： Rohan 2024-8-29

Hi,

I have a handle class with a singleton implementation that uses persistent variables.

classdef MyHandler < handle
   properties
       ...
       ...
       ...
   end
   
   methods(Access=protected)
       function obj = MyHandler()
           %Constructor logic
       end
   end
    
   methods(Static)
       function inst = instance()
           persistent obj;
           if isempty(obj)
               obj = MyPackage.MyHandler();
           end
           inst = obj;
       end
   end
    
end

Is there a way to implement the same functionality without usage of persistent variables ? I am trying to generate C code from a system object that uses this handle class.

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Answer 1

Malay Agarwal 2024-8-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2148354-singleton-implementation-without-persistent-variables#answer_1506484

编辑：Malay Agarwal 2024-8-28

在 MATLAB Online 中打开

singleton.m

Hi @Rohan,

You can create a singleton class without using persistent variables by defining the instance as a constant property. I have attached an example class to the answer. You can verify that the class indeed behaves like a singleton:

% Create two objects
obj = singleton.getInstance
obj = 
  singleton with properties:

    x: 5
    y: "Hello"
obj1 = singleton.getInstance
obj1 = 
  singleton with properties:

    x: 5
    y: "Hello"
% The two objects refer to the same handle
obj == obj1
ans = logical
   1
% Changing non-constant properties in one object reflects changes in both the objects
obj.x = 2;
obj, obj1
obj = 
  singleton with properties:

    x: 2
    y: "Hello"
obj1 = 
  singleton with properties:

    x: 2
    y: "Hello"