MATLAB Object-Oriented Programming

Observe Changes to Property Values

This example shows how to listen for changes to a property value. This example uses:

• PostSet event predefined by MATLAB


• SetObservable property attribute to enable triggering the property PostSet event.


• addlistener handle class method to create the listener

classdef PropLis < handle

% Define a property that is SetObservable

properties (SetObservable)

ObservedProp = 1

end

methods

function attachListener(obj)

%Attach a listener to a PropListener object

addlistener(obj,'ObservedProp','PostSet',@PropLis.propChange);

end

end

methods (Static)

function propChange(metaProp,eventData)

% Callback for PostSet event

% Inputs: meta.property object, event.PropertyEvent

h = eventData.AffectedObject;

propName = metaProp.Name;

disp(['The ',propName,' property has changed.'])

disp(['The new value is: ',num2str(h.ObservedProp)])

disp(['Its default value is: ',num2str(metaProp.DefaultValue)])

end

end

end

The PropLis class uses an ordinary method (attachListener) to add the listener for

the ObservedProp property. If the PropLis class defines a constructor, the constructor

can contain the call to addlistener.

The listener callback is a static method (propChange). MATLAB passes two arguments

when calling this function:

• metaProp — a meta.property object for ObservedProp


• eventData — an event.PropertyEvent object contain event-specific data.

These arguments provide information about the property and the event.

Observe Changes to Property Values