Learn Dart

main.dart

// Slashy things are single-line comments, very useful
/*
 * Slashy + star are multi-line comments
 * 
 * This is a basic inheritence example,
 * which is a core principle of OOP, or Object Oriented Programming
 */

// Imports let you use things from other libraries (code)
// that you or others have written
// This math library comes with Dart
// Most languages have an STD (lol), or a Standard Library
import 'dart:math';

// This is a list, which is the newer/cooler way of saying an Array
// This syntax uses "generics", which is a very difficult subject, but very powerful
// In this case, the List class is generic, so we need to tell it what type of list it is
// Here we're creating a list of Strings (text)
// The [square bracket] notation is used for lists/arrays, and Strings need to be quoted
List<String> meats = [
  'beef',
  'pork',
  'chicken',
];

List<String> veggies = [
  'spinach',
  'broccoli',
  'carrot',
  'lettuce',
  'tomato',
];

// Ignore this - just adding some more empty space to the output, easier to read
void log(String message) {
  print('\n$message\n');
}

// Functions can have a return type, i.e. they respond with data, or void which mean nothing
// Functions can take in arguments too
// In this case, we'll pick a random food from a given foodList
String getRandomFood(List<String> foodList) {
  // First create a new instance of Dart's Random class
  // It's good practice to declare things final if you know they won't change
  final Random random = Random();
  
  // We define the maximum number we can use, which is the size of our
  // food list + 1, since arrays start at zero
  // (so given 10 items, .length would be 10, but we can only access 0-9)
  final max = foodList.length - 1;
  
  // Now grab the next available random integer (whole number)
  // up to our maximum
  // This will return a number between 0 and max
  // This is known as the array's "index"
  int randomIndex = random.nextInt(max);
  
  // Now we send back the random food
  return foodList[randomIndex];
}

// All animals have some basic properties
// And can do some basic actions (functions)
class Animal {
  // These are some properties of Animal
  // They're final bc they can't change
  final String name;
  final String type;
  final int arms;
  final int legs;
  
  // This is a constructor. It's the main function that gets called
  // when you create a new instance of a class
  Animal(this.name, this.type, this.arms, this.legs) {
    log('HUZZAHHH, $name THE $type WAS BORN');
  }
  
  void eat(String food) {
    // When we write strings, we can use substitution by prefixing any variables with $
    log('$name ate some $food using his $arms arms, num num num num num num num');
    // can also write print('hello ' + 'world'); but that's more verbose
  }
  
  void sleep(int hours) {
    log('$name is sleaping for the next $hours hours');
  }
  
  void shit() {
    final Random random = Random();
    final shitSize = random.nextInt(5) + 1;
    log('$name took a shit that was a whopping $shitSize kg! His $legs legs almost fell off');
  }
  
  void fuck() {
    log('$name just got jiggy, allll right giggity');
    
    // Random chance he knocked her up
    final Random random = Random();
    final oneOrZero = random.nextInt(1);
    if (oneOrZero > 0) {
      log('Oh noo, $name just got his hoe preggers');
    }
  }
}

// Now let's create a more specific being by inheriting from Animal
// Dog inherits all of Animal's properties & functions
class Dog extends Animal {
  // Dog constructor also needs a name,
  // but we already know how many arms/legs it has
  // By calling super() we call the parent (Animal) class's constructor
  Dog(String name) : super(name, 'dog', 0, 4);
  
  // Here we'll override the eat function & change the message
  @override
  void eat(String food) {
    log('$name ate some $food, num num woof slobber');
  }
  
  void bark() {
    log('WOOF WOOF WOOF');
  }
  
  void barkInChinese() {
    log('WAN WAN WAN');
  }
}

// We can keep inheriting indefinitely
class GermanShephard extends Dog {
  GermanShephard(String name) : super(name);
  
  void attack() {
    log('Grrrrr arrrrr crunch $name attacked someone');
  }
}

// Most apps have some kind of main/primary entrypoint
// This function never returns anything (void), but the computer knows to run it first
void main() {
  // Let's create a dag
  final shep = GermanShephard('Adolf Barkendeutsch');
  shep.eat(getRandomFood(meats));
  shep.sleep(1);
  shep.bark();
  shep.shit();
  shep.barkInChinese();
  shep.attack();
  
  // Let's make shep eat 2 foods
  final meat = getRandomFood(meats);
  final vegg = getRandomFood(veggies);
  
  // ...and combine them into 1 string
  final shepFood = '$meat and $vegg';
  
  // ...and feed him
  shep.eat(shepFood);
  
  log('-----------------------------');
  
  // Let's create a more generic animal
  final spider = Animal('Charlotte', 'spider', 8, 8);
  spider.eat('butterfly');
  spider.sleep(12);
}