CODEWITHSUNDEEP
angulartypescriptoopsingleton
Hila Grossbard
Hila Grossbard

Reputation: 612

How to write a function that make http request and return the result of the request?

The function getEventId() is returning this.eventId.

If this.eventId == null,

  1. a function that makes an http request is being called.

  2. this.eventId = resp (the respons from the request).

    ngOnInit() { // the function bellow makes http request. this.getCustomerFileByCode().subscribe(data => { // get Id from server this.eventId = data[0]; }) }

    getEventId() { if (this.eventId) { //if the server request returned already response return of(this.eventId) } else { getCustomerFileByCode().subscrive(data =>{ this.eventId = data[0] }) // wait some how to the server response and return the value return this.eventId; }) } }

    getCustomerFileByCode(): Observable { return this.http.post(this._url, JSON.stringify(params), this.options) }

How do I return the value from the http request in the function getEventId()?

Upvotes: 0

Views: 1480

Answers (1)

Eliseo
Eliseo

Reputation: 58039

I think that you want do some like

getEventId(elementId):Observable<any> {
    if (this.eventId) { //if the server request returned already 
        return of(this.eventId)
    } else {
        return this.getCustomerFileByCode(elementId).pipe(
         map(data=>data[0]),
         tap(res => { 
            this.eventId = res;
        })
    }

And in ngOnInit

    this.getEventId(this.elementId).subscribe(()=> { 
          ...make something more...
          ...don't worry about this.eventId because the "tap" ...
          ...on the observable yet store the value...
    })

See that the getEventId return an observable, if "this.eventId" is yet, simply return of, else call to the API, transform the response -using map- and store the value -using tap-. Of course, as all observables you need subscribe to "launch". Well, you can equal teh value in subscribe and don't use "tap". But in general the observables must be declared in a service and subscribe in component, so it's more logical that the variable "belong" to the service.

Upvotes: 1

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