MATLAB: Are .m files in a subfolder of a class folder considered methods of that class

classclassdefdirectoryfolderMATLABoopparentpathpathdefprecedenceprivate

I am creating a class using the class folder approach. I understand from the MATLAB documentation that any .m file in my class folder will be treated as a method of the class.

I would like to create a subfolder within my class folder. Will .m files within this subfolder also be treated as methods of the class?

Ex. @myClass > subfolder > myMethod.m

Best Answer

Files in a subfolder of a class folder are not considered methods of the class.

Please refer to the following example:

@myClass > myClass.m:

classdef myClass
    methods
        function classObj = myClass()
            classObj.method1()
            classObj.method2()
        end
    end
end

@myClass > method1.m:

function method1(classObj)
    disp('method in class folder')
end

@myClass > subfolder > method2.m:

function method2(classObj)
    disp('method in subfolder')
end

-----

>> m = myClass
method in class folder

Unrecognized method, property or field 'method2' for class 'myClass'.

Error in myClass (line 5)

classobj.method2()

As you can see, 'method1' is part of the class, but 'method2', which is in a subfolder of '@myClass', is not treated as a method of the class.

For more details about using class folders in MATLAB, please see the following documentation page:

https://www.mathworks.com/help/matlab/matlab_oop/organizing-classes-in-folders.html

Related Solutions

MATLAB: How to call the set-dot method on a subclass object to set a property of the superclass

You cannot define a "set.xyz" method in a subclass to set the "xyz" property of the superclass. This restriction prevents a subclass from overriding a superclass implementation and cannot be bypassed. However, in some situations superclass property needs to grant subclasses the ability to participate in the setting or getting of a property value, like in this case. To do so, a superclass "set" function can call a protected method to allow subclasses to participate in property access while still maintaining some level of control.

So the implementation of the two classes might look like this:

classdef MySuperClass < handle
      properties
          xyz
      end
      methods
        function set.xyz(obj,value)
           disp(['setting xyz in MySuperClass to ', value]);
           obj.xyz = value; % updates the property
           respondToXYZChange(obj) % calls the protected method
        end 
     end 
     methods(Access = protected)
        function respondToXYZChange(obj, value) % no function definition here
        end
     end
end 
classdef MySubClass < MySuperClass
      methods
          function obj=MySubClass()
              disp('!');
          end
          function update(obj)
              disp('updating...');
          end
      end
      methods(Access = protected)
          function respondToXYZChange(obj) % call to the "update" method of subclass
              obj.update();
          end
      end
end
>> m  = MySubClass3;
!
>> m.xyz = 'a'
setting xyz in MySuperClass to a
updating...
m = 
    MySubClass3 with properties:
      xyz: 'a'
>>

Executing the command:

m.xyz = 'a';

calls the superclass "set" method which sets the value of the property "xyz" and then calls the protected "respondToXYZChange" which is defined in the subclass to call the "update" method.

MATLAB: How to change the class definition without changing the behavior of old objects (e.g. those saved in a MAT-file)

There are a number of ways that you can achieve this behavior of maintaining a single class with different behavior for different instances.

One simple approach is to use the strategy pattern:

https://en.wikipedia.org/wiki/Strategy_pattern

With this design, you can have multiple class definitions with different behaviors but the same interface, which you can define with an interface class or an interface superclass (which helps avoid code duplication).

https://www.mathworks.com/help/matlab/matlab_oop/defining-interfaces.html

e.g.

% MyClass.m
classdef MyClass < handle
    properties (Access = private)
        instance
    end
    methods
        function obj = MyClass(instance)
            if nargin < 1
                instance = MyClassV1();
            end
            obj.instance = instance;
        end
        function v = getValue(obj)
            v = obj.instance.getValue();
        end
        function v = add(obj,a,b)
            v = obj.instance.add(a,b);
        end
    end
end
------------------------------------------------
% MyClassV1.m
classdef MyClassV1 < handle
    properties
        value (1,1) double
    end
    methods
        function obj = MyClassV1()
            obj.value = 0;
        end
        function v = getValue(obj)
            v = obj.value;
        end
        function v = add(obj,a,b)
            v = a + b;
            obj.value = v;
        end
    end
end
------------------------------------------------
% MyClassV2.m
classdef MyClassV2 < handle
    properties
        value (1,1) double
    end
    methods
        function obj = MyClassV2()
            obj.value = 100;
        end
        function v = getValue(obj)
            v = obj.value;
        end
        function v = add(obj,a,b)
            v = a - b;
            obj.value = v;
        end
    end
end
------------------------------------------------
>> obj = MyClass;
>> obj.getValue()
ans =
       0
>> obj.add(1,2)
ans =
       3
>> save tmp obj
>> % change line 9 of MyClass.m to "instance = MyClassV2();"
>> clear obj
>> load tmp
>> obj.getValue()
ans =
       3
>> obj.add(1,2)
ans =
       3
>> newObj = MyClass;
>> newObj.getValue()
ans =
     100
>> newObj.add(1,2)
ans =
      -1

Best Answer

Related Solutions

MATLAB: How to call the set-dot method on a subclass object to set a property of the superclass

MATLAB: How to change the class definition without changing the behavior of old objects (e.g. those saved in a MAT-file)

Related Question