interface Food {
    name: string;
    calories: number;
    readonly x: number;
    color?: string;
}

interface LoggerInterface{
    log(arg:any):void;
}

// 函数接口
interface SearchFunc {
  (source: string, subString: string): boolean;
}

interface StringArray{
    [index: number]: string;
}
let MyArray: StringArray;
MyArray = ["是","云","随","风"];
console.log(MyArray[2]); // 随

// 普通函数
function add(a: number, b?: number): number {
  return a + b;
}

// 函数参数
function readFile(file: string, callback: (err: Error | null, data: Buffer) => void) {
  fs.readFile(file, callback);
}

// 通过 type 语句定义类型
type CallbackFunction = (err: Error | null, data: Buffer) => void;
function readFile(file: string, callback: CallbackFunction) {
  fs.readFile(file, callback);
}

// 通过 interface 语句来定义类型
interface CallbackFunction {
  (err: Error | null, data: Buffer): void;
}
function readFile(file: string, callback: CallbackFunction) {
  fs.readFile(file, callback);
}

class Menu {
  // Our properties:
  // By default they are public, but can also be private or protected.
  private items: Array<string>;  // The items in the menu, an array of strings.
  protected pages: number;         // How many pages will the menu be, a number.
  readonly other: string;

  get numOfPages(): number {
    return pages.length;
  }

  // A straightforward constructor. 
  constructor(item_list: Array<string>, total_pages: number) {
    // The this keyword is mandatory.
    this.items = item_list;    
    this.pages = total_pages;
  }

  // Methods
  public list(): void {
    console.log("Our menu for today:");
    for(var i=0; i<this.items.length; i++) {
      console.log(this.items[i]);
    }
  }

} 

// Create a new instance of the Menu class.
var sundayMenu = new Menu(["pancakes","waffles","orange juice"], 1);

// Call the list method.
sundayMenu.list();

class HappyMeal extends Menu {
  // Properties are inherited

  // A new constructor has to be defined.
  constructor(item_list: Array<string>, total_pages: number) {
    // In this case we want the exact same constructor as the parent class (Menu), 
    // To automatically copy it we can call super() - a reference to the parent's constructor.
    super(item_list, total_pages);
  }

  // Just like the properties, methods are inherited from the parent.
  // However, we want to override the list() function so we redefine it.
  list(): void{
    console.log("Our special menu for children:");
    for(var i=0; i<this.items.length; i++) {
      console.log(this.items[i]);
    }

  }
}

// Create a new instance of the HappyMeal class.
var menu_for_children = new HappyMeal(["candy","drink","toy"], 1);

// This time the log message will begin with the special introduction.
menu_for_children.list();

// The <T> after the function name symbolizes that it's a generic function.
// When we call the function, every instance of T will be replaced with the actual provided type.

// Receives one argument of type T,
// Returns an array of type T.

function genericFunc<T>(argument: T): T[] {    
  var arrayOfT: T[] = [];    // Create empty array of type T.
  arrayOfT.push(argument);   // Push, now arrayOfT = [argument].
  return arrayOfT;
}

var arrayFromString = genericFunc<string>("beep");
console.log(arrayFromString[0]);         // "beep"
console.log(typeof arrayFromString[0])   // String

var arrayFromNumber = genericFunc(42);
console.log(arrayFromNumber[0]);         // 42
console.log(typeof arrayFromNumber[0])   // number

namespace mygame{
    interface Test1Interface{
        /*...*/
    }

    export interface Test2Interface{
        /*...*/
    }
    export interface Test3Interface{
        /*...*/
    }

    export class Rect{
        /*...*/
    }

    export class Circle implements Test2Interface{
        /*...*/
    }
}