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Merge pull request kodecocodes#19 from raywenderlich/08-collections
08 collections
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‎08-collections/assets/.keep‎

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‎08-collections/projects/challenge/.keep‎

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‎08-collections/projects/challenge/challenge.dart‎

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// Copyright (c) 2020 Razeware LLC
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// For full license & permission details, see LICENSE.
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void main() {
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challenge1();
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challenge2();
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challenge3();
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}
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const paragraphOfText = 'Once upon a time there was a Dart programmer who '
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'had a challenging challenge to solve. Though the challenge was great, '
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'a solution did come. The end.';
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void challenge1() {
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/// Challenge 1: A unique request
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///
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/// Write a function that takes a paragraph of text and returns a
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/// collection of unique String characters that the text contains.
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Set<String> uniqueCodePoints(String text) {
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return text.runes
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.map((codePoint) => String.fromCharCode(codePoint))
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.toSet();
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}
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print(uniqueCodePoints(paragraphOfText));
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}
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void challenge2() {
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/// Challenge 2: Counting on you
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///
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/// Repeat Challenge 1 but this time have the function return a
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/// collection that contains the frequency count of every unique
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/// character.
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Map<String, int> characterFrequencyMap(String text) {
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final characterFrequencyMap = <String, int>{};
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for (var codePoint in text.runes) {
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final character = String.fromCharCode(codePoint);
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if (characterFrequencyMap.containsKey(character)) {
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characterFrequencyMap[character]++;
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} else {
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characterFrequencyMap[character] = 1;
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}
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}
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return characterFrequencyMap;
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}
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print(characterFrequencyMap(paragraphOfText));
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}
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void challenge3() {
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/// Challenge 3: Mapping users
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///
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/// Create a class called `User` with properties for `id` and `name`.
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/// Make a `List` with three users, specifying any appropriate names
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/// and IDs you like. Then write a function that converts your user
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/// list to a list of maps whose keys are `id` and `name`.
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final users = [
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User(1, 'Brian'),
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User(2, 'Chris'),
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User(3, 'Pablo'),
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];
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// Note: You'll find many APIs use `dynamic` instead of `Object` when
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// converting a custom object to a map. Either one works, though using
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// `Object` when possible allows you to keep type safety.
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List<Map<String, Object>> usersToMapList(List<User> users) {
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final userMapList = <Map<String, Object>>[];
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for (var user in users) {
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final userMap = {
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'id': user.id,
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'name': user.name,
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};
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userMapList.add(userMap);
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}
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return userMapList;
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}
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print(usersToMapList(users));
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}
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class User {
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User(this.id, this.name);
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final int id;
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final String name;
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}

‎08-collections/projects/challenge/mini-exercise.dart‎

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// Copyright (c) 2020 Razeware LLC
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// For full license & permission details, see LICENSE.
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void main() {
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listsMiniExercise1();
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listsMiniExercise2();
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listsMiniExercise3();
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mapsMiniExercise1();
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mapsMiniExercise2();
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mapsMiniExercise3();
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higherOrderMethodsMiniExercise1();
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higherOrderMethodsMiniExercise2();
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}
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void listsMiniExercise1() {
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/// Lists: Mini-exercise 1
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///
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/// Create an empty list of type `String`. Call it `months`. Use
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/// the `add` method to add the names of the twelve months.
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final months = <String>[];
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months.add('January');
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months.add('February');
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months.add('March');
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months.add('April');
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months.add('May');
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months.add('June');
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months.add('July');
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months.add('August');
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months.add('September');
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months.add('October');
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months.add('November');
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months.add('December');
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print(months);
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}
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void listsMiniExercise2() {
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/// Lists: Mini-exercise 2
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///
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/// Make an immutable list with the same elements as in Mini-exercise 1.
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const months = [
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'January',
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'February',
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'March',
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'April',
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'May',
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'June',
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'July',
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'August',
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'September',
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'October',
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'November',
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'December',
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];
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print(months);
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}
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void listsMiniExercise3() {
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/// Lists: Mini-exercise 3
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///
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/// Use collection `for` to create a new list with the month names in
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/// all uppercase.
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const months = [
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'January',
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'February',
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'March',
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'April',
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'May',
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'June',
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'July',
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'August',
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'September',
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'October',
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'November',
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'December',
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];
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final bigMonths = [for (var month in months) month.toUpperCase()];
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print(bigMonths);
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}
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void mapsMiniExercise1() {
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/// Maps: Mini-exercise 1
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///
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/// Create a map with the following keys: `name`, `profession`, `country`
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/// and `city`. For the values, add your own information.
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final myMap = {
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'name': 'Li Ming',
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'profession': 'software engineer',
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'country': 'China',
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'city': 'Beijing',
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};
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print(myMap);
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}
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void mapsMiniExercise2() {
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/// Maps: Mini-exercise 2
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///
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/// You suddenly decide to move to Toronto, Canada. Programmatically update
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/// the values for `country` and `city`.
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final myMap = {
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'name': 'Li Ming',
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'profession': 'software engineer',
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'country': 'China',
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'city': 'Beijing',
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};
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myMap['country'] = 'Canada';
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myMap['city'] = 'Toronto';
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print(myMap);
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}
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void mapsMiniExercise3() {
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/// Maps: Mini-exercise 3
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///
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/// Iterate over the map and print all the values.
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final myMap = {
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'name': 'Li Ming',
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'profession': 'software engineer',
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'country': 'Canada',
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'city': 'Toronto',
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};
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for (var value in myMap.values) {
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print(value);
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}
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// Or:
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myMap.forEach((key, value) => print(value));
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}
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void higherOrderMethodsMiniExercise1() {
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/// Higher order methods: Mini-exercise 1
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///
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/// Given the following exam scores:
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///
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/// ```
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/// final scores = [89, 77, 46, 93, 82, 67, 32, 88];
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/// ```
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///
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/// Use `sort` to find the highest and lowest grades.
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final scores = [89, 77, 46, 93, 82, 67, 32, 88];
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scores.sort();
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final lowest = scores.first;
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final highest = scores.last;
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print(lowest);
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print(highest);
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}
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void higherOrderMethodsMiniExercise2() {
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/// Higher order methods: Mini-exercise 2
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///
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/// Given the following exam scores:
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///
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/// ```
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/// final scores = [89, 77, 46, 93, 82, 67, 32, 88];
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/// ```
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///
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/// Use `where` to find all the B grades, that is, all the scores
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/// between 80 and 90.
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final scores = [89, 77, 46, 93, 82, 67, 32, 88];
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final bGrades = scores.where((score) => score >= 80 && score < 90);
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print(bGrades);
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}

‎08-collections/projects/final/.keep‎

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