MATLAB: Pass newly created object’s function to a timer object

classMATLABtimer

I created a class which reads a file as soon as an object is created. In order to display the progress of reading process, I created a public function (which I prefered to be private by the way). Let's call this function writeProgress,

However, after starting the timer, I receive an warning message:

"feval: Undefined function or method 'obj.writeProgress' for input arguments of type 'timer'".

The timer has been initialized like this:

t = timer('TimerFcn',@obj.writeProgress,'Period',1,'ExecutionMode','fixedDelay');

How can I pass the function "writeProgress"? Write progress needs to be a class member as it has to access private data and I'd rather prefer it to be private itself.

Best Answer

Here is a class that does what you want from the description above. The only difference is that I placed the call to writeProgeress inside of an anonymous function.

What else is different with it from your class?

classdef WP < handle
  properties 
      x
      y
  end
  methods
      function obj = WP(varargin)
          obj.x = pi;
          obj.y = 'hello world';
          t = timer('TimerFcn',@(src,evt)obj.writeProgress,'Period',1,'ExecutionMode','fixedDelay');
          start(t)
      end            
  end
  methods (Access=private)
      function writeProgress(obj)
          disp(obj.x);
          disp(obj.y);
      end
  end
end

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MATLAB: Listener callback execution error

Since handleEvnt is a method of the class RespondToToggle its first argument will be an object of type RespondToToggle. In addition, it will receive two arguments from the event, the object that triggers the event, and the event argument. Thus, the signature of the event handler should be:

function handleEvnt(obj, toggle_button_obj, ~) %obj could be replaced by ~

sidenote: for a proper OOP design State should have private write access.

MATLAB: Can timers trigger a single event that many objects listen to

Sure, that's entirely possible. You can wrap the basic MATLAB timer in an object that broadcasts an event (via the notify method). Then you can use the addlistener method within the "client" class to respond to those notifications.

Here's a basic example. This is the class that defines and broadcasts the events on a regular interval via a timer:

classdef TimerObj < handle
    properties
        theTimer
    end
    events
        TimerEvent
    end
    methods
        function this = TimerObj
            this.theTimer = timer( ...
                'ExecutionMode', 'fixedRate', ...
                'Period', 1, ...
                'TimerFcn', @(src, evt) this.notify( 'TimerEvent' ) );
            start(this.theTimer);
        end
        function delete(this)
            stop(this.theTimer);
        end
    end
end

Here's a class that can listen to those events:

classdef UserObj < handle
    properties
        Name
    end
    methods
        function this = UserObj( aName )
            this.Name = aName;
        end
        function listenToTimer(this, timerobj)
            addlistener( timerobj, 'TimerEvent', @(src, evt) this.onTimerEvent );
        end
        function onTimerEvent(this)
            disp( [this.Name ' responding to TimerEvent!'] );
        end
    end
end

Now they can be used together like this:

>> a = UserObj('Alice');
>> b = UserObj('Bob');
>> t = TimerObj;
>> a.listenToTimer(t);
Alice responding to TimerEvent!
Alice responding to TimerEvent!
>> b.listenToTimer(t)
Bob responding to TimerEvent!
Alice responding to TimerEvent!
Bob responding to TimerEvent!
Alice responding to TimerEvent!
Bob responding to TimerEvent!
Alice responding to TimerEvent!
Bob responding to TimerEvent!
Alice responding to TimerEvent!
>> delete(t)
>>

A lot of this is just a repackaging of this documentation example. So you might want to read through that, too.

Best Answer

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