firebase subscribeToTopic error

I’m not able to subscribe to a topic, below my app.ts excerpt

import "./bundle-config";
import * as app from 'application';

import * as firebase from "nativescript-plugin-firebase";

firebase.init({
    onMessageReceivedCallback: (message: firebase.Message) => {
        console.log(`Title: ${message.title}`);
        console.log(`Body: ${message.body}`);
        // if your server passed a custom property called 'foo', then do this:
        console.log(`value of 'foo': ${message.data.foo}`);
    }

}).then(
    instance => {
        console.log(`firebase.init done !! [${instance}]`);

         firebase.subscribeToTopic("/topics/musa-news").then(
            (value) => console.log("sub ok:", value),
            (reason) => console.log("sub err:", reason)
        );
    },
    error => {
        console.log(`firebase.init error: ${error}`);
    }
);

In the console I got:

JS: sub err: Can be run only after init

Probably I don’t understand when it is safe to call subscribeToTopic, the message says after init but apparently the init then() context is not such place.

[pjuros]

For me, file was firebase.nativescript.json located at the root folder of project and editing it didn’t work.

How I fixed it:

cd <root of your project>
cd node_modules/nativescript-plugin-firebase
npm run config
<this time be sure to enable Real time database>
cd <root of your project>
tns platform remove android
tns run anroid

You can check if firebase instance exists with:

firebase.init(
   {
      onPushTokenReceivedCallback: function(token) {
         console.log("app.js => onPushTokenReceivedCallback - Firebase plugin received a push token: " + token);
      },
      onMessageReceivedCallback: function(message) {
         console.log("app.js => onMessageReceivedCallback - " + JSON.stringify(message));
      }
   }).then(
      function (instance) {
         console.log("app.js => firebase.init done, instance = " + instance);
         firebase.subscribeToTopic("all").then(
            () => {console.log("app.js => subscribeToTopic(all): OK => subscribed");},
            (error) => {console.log("app.js => subscribeToTopic(all): ERROR => " + error);}
         );
      },
      function (error) {
         console.log("app.js => firebase.init error: " + error);
      }
   );

[ghost]

I had the same problem, I did some research and I found out that “firebase.instance” is null and that was caused by “com.google.firebase.database” being undefined.

How i fixed it I edited the nativescript.firebase.json and set “realtimedb” to true, after that it worked!