CODEWITHSUNDEEP
flutterdart
Karel Debedts
Karel Debedts

Reputation: 5768

Function returns an instance of Future<String> instead of String

I have a streambuilder, within, I want to calculate the distance for each different card of the streambuilder. It calculates the distance if I print it in the terminal, but on the screen it shows: Instance of future < String >. Is there a fix for this? I tried making a variable and run set state, but the value has to be different for each card of the streambuilder.

Future<String> distanceInMeters({double uLat, double uLong}) async {
  if (uLat == null && uLong == null) {
    return "";
  } else {
    double distanceInMeters =
        await Geolocator().distanceBetween(uLat, uLong, 52.3546274, 4.8285838);
    String distance = distanceInMeters.toString();
    return "$distance";
  }
}

Upvotes: 2

Views: 1556

Answers (1)

creativecreatorormaybenot
creativecreatorormaybenot

Reputation: 126604

You will need to use a FutureBuilder. If you are not familar with this widget, you can follow the link to the documentation, which describes the function of the widget extensively.

In practice, it would look something like this:

FutureBuilder(
    future: distanceInmeters(uLat: uLat, uLong: uLong),
    builder: (context, AsyncSnapshot<String> snapshot) {
      if (snapshot.hasError) return Text('${snapshot.error}');
      if (snapshot.hasData) return Text('${snapshot.data}');
      return const CircularProgressIndicator();
    },
  )

The reason you need this is that you are returning your String value from an asynchronous function and thus you need to have some logic that waits to extract the result from the Future.

Upvotes: 1

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