CODEWITHSUNDEEP
angularrxjsobservableangular-http
Chris Lang
Chris Lang

Reputation: 384

How to wait until one of many possible observables returns before continuing

I have switch statement that makes a different http call based on the input.

It looks something like this:

switch(myObject.type){
    case 'Type1':
        myObject.name = this.service1.getName(myObject.id);
        break;
    case 'Type2':
        myObject.name = this.service2.getName(myObject.id);
        break;
    case 'Type3':
        myObject.name = this.service3.getName(myObject.id);
        break;
}

and immediately after these I have a statement to save the entry:

this.storageService.saveEntry(myObject);

but at the time the entry is saved, it does not have the name property set.

What is the proper way to wait for any one of these async calls to return before saving the entry?

Upvotes: 0

Views: 415

Answers (1)

Alexander Staroselsky
Alexander Staroselsky

Reputation: 38847

If you must use the switch statement, you could perhaps have each branch return the observable instead, then set myObject.name in the subscribe() or utilize operators such as do and switchMap to pass the value to this.storageService.saveEntry(). 

foo(): Observable<any> {
    switch(myObject.type){
        case 'Type1':
            return this.service1.getName(myObject.id);
            break;
        case 'Type2':
            return this.service2.getName(myObject.id);
            break;
        case 'Type3':
            return this.service3.getName(myObject.id);
            break;
    }
}

bar() {    
    foo()
      .do(name => myObject.name = name)
      .switchMap(name => this.storageService.saveEntry(myObject))
      .subscribe(response => console.log(response);
}

Hopefully that helps!

Upvotes: 1

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