The Asset Constructor Method :: Classes and Objects (Programming)

Programming

The Asset Constructor Method

The asset class is based on a structure array with four fields:

descriptor -- Identifier of the particular asset (e.g., stock name, savings account number, etc.)
date -- The date the object was created (calculated by the date command)
type -- The type of asset (e.g., savings, bond, stock)
currentValue -- The current value of the asset (calculated from subclass data)

This information is common to asset child objects (stock, bond, and savings), so it is handled from the parent object to avoid having to define the same fields in each child class. This is particularly helpful as the number of child classes increases.

function a = asset(varargin)
% ASSET Constructor function for asset object
% a = asset(descriptor, type, currentValue)
switch nargin
case 0
% if no input arguments, create a default object
   a.descriptor = 'none';
   a.date = date;
   a.type = 'none';
   a.currentValue = 0;
   a = class(a,'asset');  
case 1
% if single argument of class asset, return it
   if (isa(varargin{1},'asset'))
      a = varargin{1};
   else
      error('Wrong argument type')
   end 
case 3
% create object using specified values
   a.descriptor = varargin{1};
   a.date = date;
   a.type = varargin{2};
   a.currentValue = varargin{3};
   a = class(a,'asset');
otherwise
   error('Wrong number of input arguments')
end

The function uses a switch statement to accommodate three possible scenarios:

Called with no arguments, the constructor returns a default asset object.
Called with one argument that is an asset object, the object is simply returned.
Called with three arguments (subclass descriptor, type, and current value), the constructor returns a new asset object.

The asset constructor method is not intended to be called directly; it is called from the child constructors since its purpose is to provide storage for common data.

Example -- Assets and Asset Subclasses The Asset get Method