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Listeners triggered even though listening to different state properties



  • I have the following logic client side

    room.listen('pullPosition/:position', (change) => {
        console.log('position', change);
        if(ready && !state.isHoldEnabled) state.setPosition(change.value)
      })
    
      room.listen('pullPosition/:hold', (change) => {
        console.log('hold', change);
      })
    

    I'm experiencing and issue where if pullPosition/:position changes BOTH listeners are triggered despite not listening to the same property.... Is this how its suppose to happen by design?


  • administrator

    (Replied on GitHub: https://github.com/gamestdio/colyseus.js/issues/42)

    Hey @karneaud, when using :anything, starting with :, it will generate a wildcard regular expression, that's why both listeners are being triggered.

    You have two alternatives on this situation, which are:

    Listening to direct properties

    room.listen('pullPosition/position', (change) => {
        console.log('position attribute has changed', change.value);
    });
    room.listen('pullPosition/hold', (change) => {
        console.log('hold attribute has changed', change.value);
    });
    

    Remember that if position is a vector, you'd need to listen to its deep variables such as x and y, by using listen('pullPosition/position/x') and listen('pullPosition/position/y'). You can also use the wildcard method for this, using the same example below.

    Listening to every attribute, and check which one has changed in the change.path

    room.listen('pullPosition/:attribute', (change) => {
        console.log(change.path.attribute, 'has changed to', change.value);
    });
    


  • Sorry to reply to an old post but this was the one that finally helped me understand how to use listen so I thought it might be helpful to clarify for other users who are as dense as I am.

    The documentation for listen at https://docs.colyseus.io/client-state-synchronization/ is painfully terse and confusing especially in how it uses the colon (:). From my understanding, if you have something like the following as your state:

    {foo: bar: {baz: 'somevalue'} }
    

    then you can listen for baz via

    room.listen('foo/bar/baz', ...)
    

    or via something like

    room.listen('foo/:wildcard_1/:wildcard-2', ...)
    

    That is you can either use the exact path or use wildcards but the text after the colon has no special meaning. I kept thinking that the :id and :attribute wildcards in the docs had a special meaning.

    Hope that helps others who got confused like me.

    Thanks again.