Duplicate subscribe messages!

[fabioaraujopt]

I'm using the following configuration:

`var ros = new ROSLIB.Ros({
url : 'ws://x.x.x.x:9090'
});

listener=new ROSLIB.Topic({
ros : ros,
name : '/vigil/sensor/gps/navsatfix',
messageType : 'sensor_msgs/NavSatFix'
});

listener.subscribe(function(message){
listener.unsubscribe();
console.log(message);
});
`
I placed the subscribe function inside a javascript setInterval, in order to call it everytime i need data, instead of being always listening to broadcast. However every time a new subscribe is done. The number of response doubles. (I think it receives all messages from begin).

first_call -> 1 log first_call -> 3 logs first_call -> 4 logs first_call -> 5 logs first_call -> 6 logs

[Rayman]

Quote from the documentation

unsubscribe(callback)

Unregisters as a subscriber for the topic. Unsubscribing stop remove all subscribe callbacks. To remove a call back, you must explicitly pass the callback function in.

callback: the optional callback to unregister, if * provided and other listeners are registered the topic won't * unsubscribe, just stop emitting to the passed listener

[fabioaraujopt]

Can you show me example? Didn't understand

[Rayman]

Something like this (not tested)

function handler(message) {
	console.log(message);
	listener.unsubscribe(handler);
}

listener.subscribe(handler);

[asvinp]

Can you show me example? Didn't understand

Hey, did you figure out the solution for this?

[ManuelZ]

@asvinp @fabioaraujopt Any solution?

I'm unsuscribing by providing the callback to the unsubscribe function but I'm ending up with an error.

[ManuelZ]

I had this issue when using React Hooks.

I was clicking a button to get subscribed and then again the same button to get unsubscribed from a topic.

• I had my topics declarations inside my component... solution, to move them out.
• I needed to memoize the function that I was using to switch the subscription on/off and as well memoize the function callback passed to topic.unsubscribe()

[asvinp]

I had this issue when using React Hooks.

I was clicking a button to get subscribed and then again the same button to get unsubscribed from a topic.

• I had my topics declarations inside my component... solution, to move them out.
• I needed to memoize the function that I was using to switch the subscription on/off and as well memoize the function callback passed to topic.unsubscribe()

@ManuelZ
If possible could you show an example?