Ionic2: platform.is() response is undefined - ionic2

Question

I'm using the native Bluetooth serial library and trying to mock data for testing in the browser. By experimentation (and a little reading) it seems that the way to do this is to check for the 'cordova' platform:
export class BluetoothServiceWrapper implements OnDestroy, OnChanges {
...
private isEmulated:boolean = true;
...
constructor(platform:Platform) {
platform.ready().then(() => {
this.isEmulated = !platform.is('cordova');
});
}
The strange thing is that this works in some parts:
connect(device:BluetoothDevice) {
return Observable.create(observer => {
...
if (!this.isEmulated) {
...
}else{
... // this is executed in the browser
}
}
}
But in other parts the this.isEmulated is undefined:
write(data:any):Promise<any> {
if (!this.isEmulated) {
return BluetoothSerial.write(data);
} else {
.... // this never gets executed
}
}
Am I overcomplicating this and there is an easier way to check if we are using browser/emulation? Or is there some error in the way the context is being passed over?
I should mention that both methods get the same members when accessing 'this' i.e. the BluetoothServiceWrapper members. In the case of the 'write' function though the isEmulated variable is hidden/undefined.

Answer 1

Ok, this was a bit of a trap. The important piece of information that was missing from the original post was that I had another component/service perform the following:
if (!this.isConnected && (!this.isConnecting)) {
this.bluetoothServiceWrapper.connect(device).subscribe(data => this.tuningModuleService.onData(data), console.error);
this.tuningModuleService.setOutputFunction(this.bluetoothServiceWrapper.write);
}
Inside the service above I would be calling this.write('somedata'), using the function above given as reference.
The service:
outputToSerialFn: any;
constructor(applicationRef: ApplicationRef, platform: Platform) {
...
// default (mock) output function
this.outputToSerialFn = function (data) {
return new Promise((resolve, reject) => {
console.log('Mock BT OUT', data);
})
};
}
setOutputFunction(outputToSerialFn: any) {
this.outputToSerialFn = outputToSerialFn;
}
The problem is that during calls the write function would get the scope of the Service using it instead of the BluetoothWrapper service.
One solution is to replace the call above with:
this.tuningModuleService.setOutputFunction(this.bluetoothServiceWrapper.write.bind(this.bluetoothServiceWrapper));
The key word is bind.
This is probably not the best pattern but might help someone who is also struggling with this. The lesson here is that passing functions as parameters overrides the original function scope.