MATLAB Object-Oriented Programming

Add Properties

The LineGraph class implements the interface defined in the GraphInterface class

and adds two additional properties—LineColor and LineType. This class defines initial

values for each property, so specifying property values in the constructor is optional. You

can create a LineGraph object with no data, but you cannot produce a graph from that

object.

properties

LineColor = [0 0 0];

LineType = '-';

end

The LineGraph Constructor

The constructor accepts a struct with x and y coordinate data, and property name/

property value pairs:

function gobj = LineGraph(data,varargin)

if nargin > 0

gobj.Data = data;

if nargin > 2

for k=1:2:length(varargin)

gobj.(varargin{k}) = varargin{k+1};

end

end

end

end

Implement the draw Method

The LineGraph draw method uses property values to create a line object. The

LineGraph class stores the line handle as protected class data. To support the use of no

input arguments for the class constructor, draw checks the Data property to determine if

it is empty before proceeding:

function gobj = draw(gobj)

if isempty(gobj.Data)

error('The LineGraph object contains no data')

end

h = line(gobj.Data.x,gobj.Data.y,...

'Color',gobj.LineColor,...

'LineStyle',gobj.LineType);

gobj.Primitive = h;

12 How to Build on Other Classes