MATLAB: Can I query the properties of a custom class using the ‘get’ method

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Can I query the properties of a custom class using the 'get' method?

Best Answer

To use the 'get' and 'set' methods for custom classes, you will first have to derive handle classes with set and get methods.

You can use the 'SetGet' mix-in to add 'get' and 'set' to a class. Once the 'get' and 'set' methods are added to the class, you can obtain the list of properties using the 'get' method:

>> h = myClass;
>> get(h)

More information regarding the mix-in is available at:

https://www.mathworks.com/help/matlab/ref/matlab.mixin.setget-class.html

Related Solutions

MATLAB: How to create custom code suggestions for class functions in MATLAB live scripts

It is possible to use code suggestions with ordinary class member functions.

The only difference is you must account for the first method argument being a reference to the class.

The first argument passed to a MATLAB class member function is a reference to the object. In that sense, the following two function calls are equivalent:

classObj.func(val)
func(classObj, val)

For more information on this, please see:

https://www.mathworks.com/help/matlab/matlab_oop/specifying-methods-and-functions.html

When creating the 'functionsSignatures.json', be sure to include an input for the class object.

Here is an example 'functionsSignature.json' snippet for a class which has static and ordinary member functions:

{
      "BasicClass.BasicClass":
      {
          "inputs":
          [
              {"name":"inputVal", "kind":"required", "type":["numeric"], "purpose":"Constructor with value to initalize with."}
          ]
      },
      "BasicClass.printString":
      {
          "inputs":
          [
              {"name":"inputString", "kind":"required", "type":["string"], "purpose":"String to print to screen."}
          ]
      },
      "BasicClass.multBy":
      {
          "inputs":
          [
              {"name":"obj", "kind":"required", "type":["BasicClass"], "purpose":"BasicClass object to run function on."},
              {"name":"multVal", "kind":"required", "type":["numeric"], "purpose":"Will multiply the initial value by multVal."}
          ]
      }
  }

In the example, "printString" is static, while "multBy" is a traditional member function.

Moreover, once you have written the JSON file, you can also verify it by executing the following command in the MATLAB Command Window:

>> validateFunctionSignaturesJSON

You will find more information about this function in the documentation:

https://www.mathworks.com/help/matlab/ref/validatefunctionsignaturesjson.html

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.

Best Answer

Related Solutions

MATLAB: How to create custom code suggestions for class functions in MATLAB live scripts

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

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