kwalrath

class C {
  int? i;                  // (1)
  void f() {
    if (i == null) return;
    print(i.isEven);       // (2) ERROR
  }
}

kwalrath

import 'dart:math';

abstract class Shape {
  factory Shape(String type) {
    if (type == 'circle') return Circle(2);
    if (type == 'square') return Square(2);
    throw 'Can\'t create $type.';
  }
  num get area;
}

kwalrath

import 'dart:math' show Random;

main() async {
  print('Compute π using the Monte Carlo method.');
  await for (final estimate in computePi().take(100)) {
    print('π ≅ $estimate');
  }
}

/// Generates a stream of increasingly accurate estimates of π.

kwalrath

main() {
  int anInt; // Declared but not initialized... yet.
  anInt = 1; // Try commenting out this line.
  print('The value of anInt is $anInt.');
}

kwalrath

// Copyright 2019 the Dart project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file.

// Try using `?`, `!`, and `late` to clean up the analysis
// errors in this code!
class MyClass {
  late int val; 
  
  // Sometimes I get an error: Non-nullable instance field 'val'

kwalrath

class WannabeFunction {
  String call(String a, String b, String c) => '$a $b $c!';
}

var wf = WannabeFunction();
var out = wf('Hi', 'there,', 'gang');

main() => print(out);

kwalrath

final subscription = myStream.listen(
  (data) {
    print('Data: $data');
  },
  onError: (err) {
    print('Error!');
  },
  cancelOnError: false,
  onDone: () {
    print('Done!');

kwalrath

final subscription = myStream.listen(...);

subscription.pause();
subscription.resume();
subscription.cancel();

kwalrath

NumberCreator().stream
    .where((i) => i % 2 == 0)
    .map((i) => 'String $i')
    .listen(print);
/*
OUTPUT:
String 2
String 4
String 6
String 8

kwalrath

NumberCreator().stream
    .map((i) => 'String $i')
    .listen(print);
/*
OUTPUT: 
String 1
String 2
String 3
String 4
*/