An example dealing with multiple write requests would be very helpful

[DanielO]

Hi, I am a JS noob and would really appreciate a sample demonstrating how to implement queuing or retries for writeValue requests. I get "NetworkError: GATT operation already in progress." (i.e. https://github.com/WebBluetoothCG/web-bluetooth/issues/188) when trying to write a non-trivial app that has user driven writes.

[beaufortfrancois]

Hello @DanielO, here's below some JS snippet that might help you.

navigator.bluetooth.requestDevice({filters: [{services: ['heart_rate']}]})
.then(device => device.gatt.connect())
.then(server => server.getPrimaryService('heart_rate'))
.then(service => service.getCharacteristic('heart_rate_control_point'))
.then(characteristic => resetEnergy(characteristic, 3 /* tries */)))
.then(_ => {
  console.log('Energy expended has been reset.');
 })
.catch(error => {
  log('Argh! ' + error);
});

function resetEnergy(characteristic, leftTries) {
  // Writing 1 is the signal to reset energy expended.
  let resetEnergyExpended = Uint8Array.of(1);
  return characteristic.writeValue(resetEnergyExpended)
  .catch(error => {
     leftTries--;
     if (leftTries > 0) {
       return resetEnergy(characteristic, leftTries);
     }
     return Promise.reject(error);
  });
}

[DanielO]

Ahh, that looks good thanks!

I actually ended up creating a message queue using https://github.com/d3/d3-queue which is probably overkill..

Do you think it's worth adding to the docs? Or is it there and I missed it? (quite possible :)

[hardillb]

This example shows how to retry one write over and over. I'm struggling to see how to queue up multiple writes. Any chance of any updated example?

[DanielO]

@hardillb It's been a while so I've paged this out but my code is at https://bitbucket.org/DJOConnor/mooshiweb/src/default/ if you want to poke around.

[conde2]

I'm facing the same problem, need to do a lot write operations and getting this error

ERROR Error: Uncaught (in promise): NetworkError: GATT operation already in progress.

@DanielO The link is broken, could you share the code again ?

[DanielO]

How about - https://hg.sr.ht/~darius/mooshiweb/browse

[conde2]

I manage doing it with a simple array and promises, thanks

  tasks: Function[] = [];

  async addTask(task) {
    const previousTaskCount = this.tasks.length;
    this.tasks.push(task);

    if (previousTaskCount === 0) {
      this.runTasks();
    }
  }

  async runTasks() {
    if (this.tasks.length <= 0) {
      return true;
    }

    while(this.tasks.length > 0) {
      const task: Function = this.tasks[0];
      try {
        await task.call(this);
        this.tasks.shift();
      } catch (error) {
        console.log("Error:", error);
      }
    }
  }