Angular 5 HttpClient 'get' call returns array if 2+ results but not an array on 1 result

Question

On my test Angular 5 web client, on this HTTP call to my Java Jax-RS REST server I expect a return of data as array of type - PlayerRecord. (It is a simple class with a few fields).

 this.http.get<PlayerRecord[]>(this.url)
        .subscribe(data => this.onDataSuccess(data), 
                    err => this.errorHttp.set(err));

I am handling the data in the below function with parameter that expects data to be again an array of type - PlayerRecord:

playerRst: PlayerRecord[];

private onDataSuccess (data: PlayerRecord[]) {
    this.playerRst = data;
    console.log(this.playerRst.length);
    console.log(this.playerRst[0]);
    ...
}

Now, if the result has 2 or more elements in the array, I do get the expected array of data fine, HOWEVER, if I get only 1 record from the server, 'data' is no more an array and the steps in the onDataSuccess function fail.

Can you please explain why TypeScript can't keep an 1 element array as array or what I am missing, and how to work around this? Thank you.

Can you please include the response data.

Brad
– Brad

2018-01-21 22:24:27 +00:00
Commented Jan 21, 2018 at 22:24 — Brad
– Brad, Commented Jan 21, 2018 at 22:24
99% that its server is sending one object instead of array.

alexKhymenko
– alexKhymenko

2018-01-21 22:24:59 +00:00
Commented Jan 21, 2018 at 22:24 — alexKhymenko
– alexKhymenko, Commented Jan 21, 2018 at 22:24

Asura · Accepted Answer · 2018-01-21 22:25:55Z

2

The problem is likely your backend.

If a query such as get player record can returns multiple records then your backend should return a list even if that list contains a single element otherwise you will have problem like this due to response being parsed.

It doesnt make any sense to have a service call that sometime returns a single object and other time a list of object and then angular expecting an array of object to map.

answered Jan 21, 2018 at 22:25

Asura

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1 Comment

Felix Over a year ago

Good point. I should have looked a at the server end, what it returns. Thanks.

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