samples/platform_design/lib/utils.dart

import 'dart:math';

import 'package:english_words/english_words.dart';
// This reimplements generateWordPair because english_words's
// implementation has some performance issues.
// https://github.com/filiph/english_words/issues/9
// ignore: implementation_imports
import 'package:english_words/src/words/unsafe.dart';
import 'package:flutter/material.dart';

// This file has a number of platform-agnostic non-Widget utility functions.

const _myListOfRandomColors = [
  Colors.red,
  Colors.blue,
  Colors.teal,
  Colors.yellow,
  Colors.amber,
  Colors.deepOrange,
  Colors.green,
  Colors.indigo,
  Colors.lime,
  Colors.pink,
  Colors.orange,
];

final _random = Random();

final wordPairIterator = generateWordPair();
Iterable<WordPair> generateWordPair() sync* {
  bool filterWord(String word) => unsafe.contains(word);
  String pickRandom(List<String> list) => list[_random.nextInt(list.length)];

  String prefix;
  while (true) {
    if (_random.nextBool()) {
      prefix = pickRandom(adjectives);
    } else {
      prefix = pickRandom(nouns);
    }
    final suffix = pickRandom(nouns);

    if (filterWord(prefix) || filterWord(suffix)) continue;

    final wordPair = WordPair(prefix, suffix);
    yield wordPair;
  }
}

String generateRandomHeadline() {
  final artist = capitalizePair(wordPairIterator.first);

  switch (_random.nextInt(10)) {
    case 0:
      return '$artist says ${nouns[_random.nextInt(nouns.length)]}';
    case 1:
      return '$artist arrested due to ${wordPairIterator.first.join(' ')}';
    case 2:
      return '$artist releases ${capitalizePair(wordPairIterator.first)}';
    case 3:
      return '$artist talks about his ${nouns[_random.nextInt(nouns.length)]}';
    case 4:
      return '$artist talks about her ${nouns[_random.nextInt(nouns.length)]}';
    case 5:
      return '$artist talks about their ${nouns[_random.nextInt(nouns.length)]}';
    case 6:
      return '$artist says their music is inspired by ${wordPairIterator.first.join(' ')}';
    case 7:
      return '$artist says the world needs more ${nouns[_random.nextInt(nouns.length)]}';
    case 8:
      return '$artist calls their band ${adjectives[_random.nextInt(adjectives.length)]}';
    case 9:
      return '$artist finally ready to talk about ${nouns[_random.nextInt(nouns.length)]}';
  }

  assert(false, 'Failed to generate news headline');
  return null;
}

List<MaterialColor> getRandomColors(int amount) {
  return List<MaterialColor>.generate(amount, (index) {
    return _myListOfRandomColors[_random.nextInt(_myListOfRandomColors.length)];
  });
}

List<String> getRandomNames(int amount) {
  return wordPairIterator
      .take(amount)
      .map((pair) => capitalizePair(pair))
      .toList();
}

String capitalize(String word) {
  return '${word[0].toUpperCase()}${word.substring(1).toLowerCase()}';
}

String capitalizePair(WordPair pair) {
  return '${capitalize(pair.first)} ${capitalize(pair.second)}';
}