MATLAB Object-Oriented Programming

Concrete methods defined by superclasses in a heterogeneous hierarchy must specify the

Sealed attribute. Sealing these methods prevents subclasses from overriding methods

implemented by the superclass. When calling methods on a heterogeneous array,

MATLAB calls the methods defined by the class of the array (Assets in this example).

The pie and makeReport methods are examples of sealed methods that operate on

heterogeneous arrays composed of Stock, Bond, and Cash objects.

Abstract methods defined by the superclasses in a heterogeneous hierarchy must specify

the Abstract attribute. Defining an abstract method in a superclass ensures that

concrete subclasses have an implementation for that exact method name. Use these

methods element-wise so that each object calls its own method.

The getCurrentValue method is an example of an abstract method that is implemented

by each subclass to get the current value of each asset.

Each type of subclass object calculates its current value in a different way. If you add

another category of asset by adding another subclass to the hierarchy, this class must

implement its own version of a getCurrentValue method. Because all subclasses

implement a getCurrentValue method, the pie and makeReport methods work with

newly added subclasses.

For more information on the Sealed and Abstract method attributes, see “Method

Attributes” on page 9-5.

Assets Class Code

The Assets class and other classes in the hierarchy are contained in a package called

financial.

classdef Assets < matlab.mixin.Heterogeneous

% file: +financial.@Assets/Assets.m

properties

Description char = 'Assets'

end

properties (Abstract, SetAccess = private)

Type

end

methods (Abstract)

% Not implemented by Assets class

value = getCurrentValue(obj)

end

methods (Static, Sealed, Access = protected)

20 Designing Related Classes