Initialize Objects When Loading

Calling Constructor When Loading Objects

MATLAB^® does not call the class constructor when loading an object from a MAT-file. However, if you set the ConstructOnLoad class attribute to true, load does call the constructor with no arguments.

Enable ConstructOnLoad when you do not want to implement a loadobj method, but must perform some actions at construction time. For example, enable ConstructOnLoad when you are registering listeners for another object. Ensure that MATLAB can call the class constructor with no arguments without generating an error.

Attributes set on superclasses are not inherited by subclasses. Therefore, MATLAB does not use the value of the superclass ConstructOnLoad attribute when loading objects. If you want MATLAB to call the class constructor, set the ConstructOnLoad attribute in your specific subclass.

If the constructor requires input arguments, use a loadobj method.

Initializing Objects in the `loadobj` Method

Use a loadobj method when the class constructor requires input arguments to perform object initialization.

The LabResults class shares the constructor object initialization steps with the loadobj method by performing these steps in the assignStatus method.

Objects of the LabResults class:

Hold values for the results of tests.
Assign a status for each value based on a set of criteria.

classdef LabResult
   properties
      CurrentValue
   end
   properties (Transient)
      Status
   end
   methods
      function obj = LabResult(cv)
         obj.CurrentValue = cv;
         obj = assignStatus(obj);
      end
      function obj = assignStatus(obj)
         v = obj.CurrentValue;
         if v < 10
            obj.Status = 'Too low';
         elseif v >= 10 && v < 100
            obj.Status = 'In range';
         else
            obj.Status = 'Too high';
         end
      end
   end
   methods (Static)
      function obj = loadobj(s)
         if isstruct(s)
            cv = s.CurrentValue;
            obj = LabResults(cv);
         else
            obj = assignStatus(s);
         end
      end
   end
end

The LabResults class uses loadobj to determine the status of a given test value. This approach provides a way to:

Modify the criteria for determining status
Ensure that objects always use the current criteria

You do not need to implement a saveobj method.

Documentation