CODEWITHSUNDEEP
dart
Ajay Gautam
Ajay Gautam

Reputation: 1023

Dart streams - skipWhile not skipping events

Doesn't seem like skipWhile is doing anything... or am I understanding this wrong?

Below code... I am expecting skipWhile to remove two entries!

Dart version (from flutter doctor): Dart version 2.9.0 (build 2.9.0-10.0.dev 7706afbcf5)

import 'package:flutter_test/flutter_test.dart';

class Car {
  final String name;
  final bool active;
  final int wheels;

  Car({this.name, this.active=true, this.wheels=4});
}

void main() {
  test("Check skipWhile", () {
    List dataSet = [
      Car(name: "Thunder", active: false),
      Car(name: "Lightening", active: false),
      Car(name: "Dinky", wheels: 3),
      Car(name: "Camry"),
      Car(name: "Outback"),
    ];

    List activeCars = dataSet.skipWhile((car) => car.active).toList();

    expect(activeCars.length, 3);
  });
}

Upvotes: 0

Views: 809

Answers (1)

julemand101
julemand101

Reputation: 31219

If you read the documentation for skipWhile you will see:

Returns an Iterable that skips leading elements while test is satisfied.

So it just skips the leading elements and not all elements.

What you properly want instead is where which does:

Returns a new lazy Iterable with all elements that satisfy the predicate test.

So if I change your skipWhile to where in your example, I will now get the length of 3:

class Car {
  final String name;
  final bool active;
  final int wheels;

  Car({this.name, this.active = true, this.wheels = 4});
}

void main() {
  final dataSet = [
    Car(name: "Thunder", active: false),
    Car(name: "Lightening", active: false),
    Car(name: "Dinky", wheels: 3),
    Car(name: "Camry"),
    Car(name: "Outback"),
  ];

  final activeCars = dataSet.where((car) => car.active).toList();

  print(activeCars.length); // 3
}

Upvotes: 2

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