Angular 6 observables - extract data from .subscribe() function and use it elsewhere
Solution 1
just return the HTTP req from getData()
and subscribe it inside the workbookInit
function.
getData2() {
return this.m_dbService.get('api/myApiPath')
}
workbookInit(args){
this.getData2().subscribe(
data => {
var datasource = data
},
error => { throw error },
() => console.log("finished")
}
Solution 2
What you probably want to do is to populate another Observable
with the data so that you can access it elsewhere in your project without the need for calling the API more than once.
To do this, you create what is known as a Subject
(in this case a BehaviorSubject
) and you can populate that with data when your API call returns a response.
Then, in order to access this data elsewhere, you can create a "get" function to return the Subject
(which is itself an Observable
) whenever you need the data.
Here is an example:
my-data.service.ts
myData: BehaviorSubject<number> = new BehaviorSubject<number>(0);
callApi() {
this.dbService.get('apiUrl').subscribe(
(data) = > this.myData.next(data) // Assuming data is a 'number'
);
}
getMyData() {
return this.myData.asObservable();
}
Now to use this in a component:
this.myService.getMyData().subscribe(
(data) => { /* Use the value from myData observable freely */ }
);
Or you could rely on the Angular async pipe (which is a very convenient method for dealing with observables in your code).
Solution 3
You should not subscribe to the Observable
inside getData2
. Return it as is instead, then do the following:
var dataSource;
this.getData2().subscribe(res => dataSource = res);
Please note that the variable dataSource
will be set when the request is done (asynchronously), so you can't use it immediately in the same block scope.
If you want to use it immediately, then put your code inside the subscription.
Solution 4
If you have an observable that provides data to populate a table, the best way is not to use subscribe()
, but use the observable directly in your html template by using the async
pipe. You'll have less to worry about and your code will be much simpler.
Kyle Vassella
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Updated on June 18, 2022Comments
-
Kyle Vassella almost 2 years
I'm banging my head against the wall with observables. Almost all of the documentation I can find is in the older
rxjs
syntax.I have an API call which is an observable. I'm calling it elsewhere and subscribing to it - trying to populate a table with the data from this
GET
request.If I simply
console.log
mygetData
function, it logs the subscription rather than my data. I can successfully console.logdata
within the.subscribe
function, but I want to usedata
outside of.subscribe()
.How do I extract
data
out of the.subscribe()
function and use it elsewhere? Or, must all of my logic be contained within the.subscribe()
function to usedata
?getData2() { return this.m_dbService.get('api/myApiPath').subscribe( data => (console.log(data)), //This properly logs my data. How to extract `data` out of here and actually use it? error => { throw error }, () => console.log("finished") ); } workbookInit(args){ var datasource = this.getData2(); // this returns the subscription and doesn't work. }