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    Ajay.Gov
    @ajay-gov
    @vishnuprasad73_twitter the oldValue is being assigned before you call valueLane.set. So the oldValue has the initial value of the valueLane which is Absent (indicates that it is absent).
    let oldvalue = valueLane.get();
    valueLane.set("john");
    console.log(oldvalue);
    oldvalue = valueLane.get();
    console.log(oldvalue);
    This should print Absent and then "john".
    valueLane.get() returns the current value of that valueLane()
    Vishnu Prassad
    @vishnuprasad73_twitter

    @ajay-gov got it. what im trying to achieve is, to get the old and new value on the client side.

    on the server side,

      @SwimLane("info")
      ValueLane<String> info = this.<String>valueLane()
          .didSet((newValue, oldValue) -> {
            logMessage("`info` set to " + newValue + " from " + oldValue);
          });

    this prints the old and new value every time i set a new value. like this, [/welcome/user]infoset to hello from world

    but on client side,

    .didSet((newValue, oldValue) => {
                            console.log("link watched info change to " + newValue + " from " + oldValue);
                          })

    this always comes as absent.

    Maybe I'm understanding the purpose of value lane incorrectly?

    Vishnu Prassad
    @vishnuprasad73_twitter
    is there a way to get the current remote state? that i can show as old value while setting new value
    Ajay.Gov
    @ajay-gov

    @vishnuprasad73_twitter

    const client = new swim.WarpClient();
    
    let valueLane = client.downlinkValue()
                        .hostUri("warp://localhost:9001").nodeUri("/welcome/user").laneUri("info")
                        .didSet((newValue, oldValue) => {
                            console.log("link watched info change to " + newValue + " from " + oldValue);
                          })
                        .open();

    is all you need. Whenever the "info" lane for the node "/welcome/user" gets updated on the server then the didSet callback in the valueLane reference in the client should get invoked with the oldValue and the newValue. Are you not seeing this?

    Vishnu Prassad
    @vishnuprasad73_twitter

    @ajay-gov i tried that. but when i set a new value, the callback im getting on the client side is,
    link watched info change to john from Value.absent()

    i have the same callback on server side, which works correctly.

    @SwimLane("info")
      ValueLane<String> info = this.<String>valueLane()
          .didSet((newValue, oldValue) -> {
            logMessage("`info` set to " + newValue + " from " + oldValue);
          });

    which logs out put as below,

    [/welcome/user] `info` set to doe from john

    i tried setting the value as @scottswim mentioned above, valuelane.set(swim.Value.fromAny("john")) still it shows as absent on client side though
    Ajay.Gov
    @ajay-gov
    hmm..strange that it's not working. How are you setting the value lane i.e is it done on the server side? Also hopefully you are not calling client.close() before the value lane gets set.
    Vishnu Prassad
    @vishnuprasad73_twitter
    Ohhh!. I was calling client.close() at the end of the code!. Removed it and now i can see the old value though.
    @ajay-gov
    Ajay.Gov
    @ajay-gov
    @vishnuprasad73_twitter Great, so it works now?
    Vishnu Prassad
    @vishnuprasad73_twitter
    Yes. Thank a lot.
    Vishnu Prassad
    @vishnuprasad73_twitter
    @ajay-gov Do you know any services or any simulator which provides sample IoT data which i can use and play around with swim ?
    Ajay.Gov
    @ajay-gov
    Sure, glad to hear that it works. A bit more detail- when you open a downlink the swim client establishes a connection to the server. The data is streamed from the server to the client using that connection. You may open multiple downlinks i.e to other nodes/lanes on the same host and the swim client will use the same connection to stream data to the different downlinks. However when you call client.close the connection to the server is closed and all downlinks will stop getting the data from the server.
    Ajay.Gov
    @ajay-gov
    @vishnuprasad73_twitter we work with customer related data for our enterprise apps. We have built a couple of sample apps that use public data sources.
    1. Swim Transit (Repo for code here: https://github.com/swimos/transit) is a real-time application that uses bus location information from multiple cities in the US. The bus location is sent from sensors on these buses. The docs for their API is here: https://gist.github.com/grantland/7cf4097dd9cdf0dfed14. You can look at the https://github.com/swimos/transit code to see how you can create web-agents from it and then build a real-time streaming web application using those web agents from a REST API data source.
    2. Swim Flight Tracker is a real-time application that uses flight location information. The flight location information is available here: https://opensky-network.org/apidoc/
    Vishnu Prassad
    @vishnuprasad73_twitter
    @ajay-gov Thanks again.SWIM is really interesting :) Does swim have any plans to have support for the server-side in other languages other than Java?
    Vishnu Prassad
    @vishnuprasad73_twitter
    Im a noob at Java, Learned a bit of basic of it for SWIM. :)
    Ajay.Gov
    @ajay-gov
    @vishnuprasad73_twitter We are working on moving the swim-core into Rust. Since Rust will run natively, we plan on supporting other language bindings into Rust. At that point you could use other languages on the server-side
    @vishnuprasad73_twitter Glad you like swim! Please do spread the word.
    Scott Clarke
    @scottswim
    you can find the source for the Flight Tracker demo here https://github.com/swimos/flight-tracker. It demos using both 3rd party APIs (OpenSky) as well as static CSV files. The project itself is split into 2 parts. The main webapp and a data simulator. The data simulator takes data from the APIs and CSV files and sends data into the main app in a timed way using swim command lanes. This allows for starting/stopping/replaying the data in the main app.
    We also have a simpler demo where we use NodeJS to bridge sensor data from an Arduino into Swim. The code for that demo is here: https://github.com/swimos/plant-monitor
    Pasquale Vazzana
    @Pasvaz
    @scottswim are you guys aware that the flight-tracker doesn't work on Safari?
    Brad Johnson
    @johnson_brad_twitter
    Hey @Pasvaz - just tagged @scottswim and some of our other devs in Slack. I think it's a known issue?
    Scott Clarke
    @scottswim
    I was just made aware of that a few days ago :D I have not had a chance to fix it yet.
    Pasquale Vazzana
    @Pasvaz
    I'll check the code and see if it's a real issue, it doesn't seem to like Classes but afaik Safari supports classes since v9
    Scott Clarke
    @scottswim
    thanks for letting us know.
    Pasquale Vazzana
    @Pasvaz
    no I stand corrected, classes are supported but no public/private fields, which is where it complains indeed
    Scott Clarke
    @scottswim
    yeah, safari does not like how i am doing member vars in the class.
    Pasquale Vazzana
    @Pasvaz
    yeah
    Scott Clarke
    @scottswim
    should be an easy enough fix, just have not had the time just yet.
    Pasquale Vazzana
    @Pasvaz
    I guess only babel can, there is no way to make Safari use public members apart transpiling them
    anyway, it's not a major issue, Chrome works fine
    Scott Clarke
    @scottswim
    firefox works as well.
    Pasquale Vazzana
    @Pasvaz
    not on android apparently
    Scott Clarke
    @scottswim
    oh, yeah, i am not surprised there. I have not done any optimization for mobile for flight-tracker
    that is another good thing to add to the list however.
    mobile support should be fairly easy to add.
    Scott Clarke
    @scottswim
    thanks.
    really this is where things like babel are perfect, however i am not using it in the project because i wanted to keep things as simple as possible.
    Pasquale Vazzana
    @Pasvaz
    I know what you mean
    Ajay.Gov
    @ajay-gov
    @Pasvaz thanks for pointing the issue with the flight tracker. traffic (https://github.com/swimos/traffic), transit (https://github.com/swimos/transit) work on safari and on android.
    https://traffic.swim.ai/ and https://transit.swim.ai/ are the hosted versions of those repos respectively
    Scott Clarke
    @scottswim
    flight tracker should be working better now in safari too.
    just pushed some quick fixes for safari to github and the live demo site.
    Pasquale Vazzana
    @Pasvaz
    Thanks @ajay-gov @scottswim
    Pasquale Vazzana
    @Pasvaz
    transit is quite cool and probably a better place to start
    Ajay.Gov
    @ajay-gov
    @Pasvaz thanks. Please do ping us if you have any questions.
    Peace Michaels
    @oexza

    Hi @ajay-gov

    I am a two day old swimer, so the workings of swim are not yet very clear to me. I'm exploring the possibility of using a webagent as single writer per stream in an eventstore.

    How does one co-ordinate planes in such a manner that only one instance of a webagent can exist in a "cluster" of servers, and ensure that requests are routed/re-routed to the node that has that instance running? this would be kind of like what you can achieve with Akka Cluster Sharding. Is this possible with swim?