Protected constructor vs abstract class

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behzad abdollahikhameneh 2018-3-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/388709-protected-constructor-vs-abstract-class

编辑： per isakson 2018-3-17

在 MATLAB Online 中打开

Is there a difference between

1. Define constructor as Protected.

2. Define a class "Abstract" to avoid direct instantiation (only subclasses can be instantiated)

Example:

classdef (Abstract) TestInterface < handle
  properties
      test;
  end
  methods (Abstract)
         testMethod(pObj);
         testMethod2(pObj);
  end 
end
classdef  TestImpl < TestInterface     %%%%%%%%%%%%%VARIATION 1
  methods       
      function testMethod(pObj)              
      end
  end  
    methods(Access = 'protected')
        function rObj = TestImpl()
            rObj.test = 1;
        end
    end
end
classdef (Abstract) TestImpl < TestInterface      %%%%%%%%%%%%VARIATION 2
    methods       
        function rObj = TestImpl()
            rObj.test = 1;
        end
        function testMethod(pObj)              
        end
    end  
end
classdef  TestImpl2 < TestImpl
  methods  
        function rObj = TestImpl2()
            rObj = rObj@TestImpl();
        end
        function testMethod(pObj)
        end
        function testMethod2(pObj)
        end
    end  
end

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per isakson 2018-3-17

编辑：per isakson 2018-3-17

"Define constructor as Protected [or private]." doesn't make the class abstract. Combined with static methods it may be used to implement the Singleton Pattern.

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