Warning... Very long message...
So I changed one of the observables to a promise because it could work as a
promise as well and all is working well now, as far as I can tell.
Do you see anything wrong with my approach?
// single http get call turning into a promise
getDataP(): Promise<Array<string>> {
return this.http.get(*url*).toPromise();
}
// one observable that reads a configFile
getConfigurationSettings(url) : Observable<string[]> {
return this.http.get(url)
.map((res:Response) => {
return res.json()
})
.catch((error:any) => Observable.throw(error.json().error ||
'Failed to get flowsheet configuration settings'));
}
// another http get call as an observable...
// this also can be made into a promise but it is fine for now
// just one http get call
askForPatientContextWSAddress() : Observable<string[]> {
return this.http.get(this.patientContextProviderURL)
.map((res:Response) => {
return ['ws://localhost:3006'];
})
.catch((error: Response | any) => {
if (error instanceof Response && error.status !== 200) {
console.log('failed to get valid response code:' + error.status
+ 'error text: ' + error.text());
}
return Observable.throw(error);
})
}
//code to call the http get call every 15 sec
startGettingData () {
setInterval(
console.log('startGettingData');
this.getDataP().then(function (stringArray) {
console.log(stringArray);
return stringArray;
}), 15000);
}
// observable to listen for websocket messages
// and process them
processWebscoketMessages(): Observable<any>{
console.log('listenForContextChanges');
return Observable.fromEvent(this.contextWS,'message')
.map(res=>"From WS: " + res.data);
}
// just a test observable code to generate a value every second
var numbers = Observable.interval(1000);
// the final combination of promises and observables...
this.getConfigurationSettings()
.do(config => {
// nothing async
console.log('we got the configuration settings.');
this.configSettings = config;
})
.switchMap(res => this.askForPatientContextWSAddress())
.do(x => {
// nothing async
// construct the webscoket...
this.contextWS = new WebSocket(wsAdress);
this.contextWS.onopen = (evt) => {
this.contextWS.send("Hello World");
};
})
.switchMap(r => this. processWebscoketMessages())
// in the following do block/side effect, I start the timer based call to
the
// http get promise.
.do (() => this.startGettingData())
.merge(numbers)
.subscribe(
x => {
console.log(*'got data');*
* // process the data, synchronous.* },
err => {
// Log errors if any
console.log(err);
},
() => console.log('app exiting'));
How does the following structure look like?
On Thursday, April 20, 2017 at 10:25:28 PM UTC-7, Sander Elias wrote:
>
> Hi Reza,
>
> Well, as usual, it depends on what you need to do. But if you have indeed
> 2 different observables, that result in 2 different things, that need
> different handling, then you have a reason to use multiple subscribers.
> But be careful with side-effects. Observables work great if you use pure
> functions. But if you mix in side-effect, debugging them becomes a
> nightmare. If you need side-effect, make sure they are putting things out,
> not pulling things in. Does that make sense to you?
>
> Regards
> Sander
>
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