MATLAB: Anyone listening for a particular event

dynamicpropseventshandlelistenerMATLABoop

Hi,
I have an object that can fire many events, and computing the events takes a significant amount of time. Therefore, I would like to compute the events only if I know there is someone listening for them.
Is there any way for the object to get notified when a listener is added or removed? Is there any way to get the list of current listeners? Is there any way to check the count of active listeners for a given event?
Thanks, Joan

Best Answer

@Joan, This is an interesting problem! I don't know what the ideal solution is, but maybe you could create three classes: subscriber, contract and broker. The broker class would manage the other two. It would behave something like this:
  • Maintain a structure marketFeeds with dynamic fields feedname. Each field has two subfields: subscriberHandle and listenerHandle.
  • Input handle to new contract ( broker.addContract(contractHandle) ).
For each feed name, see if it is one of the field names in marketFeeds.
If it exists, add contractHandle to list of handles maintained by the corresponding listener ( i.e., listenerHandle.addContract(marketFeeds.feedName.contractHandle)).
If it doesn't exist, add a new subscriber object and a listener for that object. Give the handle of the contract to the listener.
When a listener is told of a change in the market feed, it calls each of the handles with some command like contractHandle.reactToMarketChange(feedName,NewValue).
When the contract is terminated, send its handle to broker.deleteContract, which then does all the necessary actions on marketFeeds.
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