Types

• Boolean
• Number
• String
• Array
• Tuple
• Enum
• Any
• Void
• *Union

Boolean

Number

String

Array

Tuple

Enum

Any

Void

Union 

let foo : string | boolean;

foo = true;
foo = "true";

foo = 1; //Error!

Classes

Inheritence

Public

Public is the default accessor.

//These are equivalent
class Animal {
    public name: string;
    public constructor(theName: string) { this.name = theName; }
    public move(distanceInMeters: number) {
        console.log(`${this.name} moved ${distanceInMeters}m.`);
    }
}

class Animal {
    name: string;
    constructor(theName: string) { this.name = theName; }
    move(distanceInMeters: number) {
        console.log(`${this.name} moved ${distanceInMeters}m.`);
    }
}

Private

Cannot be used outside the class.

class Animal {
    private name: string;
    constructor(theName: string) { this.name = theName; }
}

new Animal("Cat").name; // Error: 'name' is private;

Protected

Protected acts much like the private modifier with the exception that members declared protected can also be accessed by instances of deriving classes

class Person {
    protected name: string;
    constructor(name: string) { this.name = name; }
}

class Employee extends Person {
    private department: string;

    constructor(name: string, department: string) {
        super(name);
        this.department = department;
    }

    public getElevatorPitch() {
        return `Hello, my name is ${this.name} and I work in ${this.department}.`;
    }
}

let howard = new Employee("Howard", "Sales");
console.log(howard.getElevatorPitch());
console.log(howard.name); // error

Static

class Grid {
    static origin = {x: 0, y: 0};
    calculateDistanceFromOrigin(point: {x: number; y: number;}) {
        let xDist = (point.x - Grid.origin.x);
        let yDist = (point.y - Grid.origin.y);
        return Math.sqrt(xDist * xDist + yDist * yDist) / this.scale;
    }
    constructor (public scale: number) { }
}

let grid1 = new Grid(1.0);  // 1x scale
let grid2 = new Grid(5.0);  // 5x scale

console.log(grid1.calculateDistanceFromOrigin({x: 10, y: 10}));
console.log(grid2.calculateDistanceFromOrigin({x: 10, y: 10}));

Abstract Classes

abstract class Department {
    constructor(public name: string) {}
    printName(): void {
        console.log('Department name: ' + this.name);
    }
    abstract printMeeting(): void; // must be implemented in derived classes
}

class AccountingDepartment extends Department {
    constructor() {
        super('Accounting and Auditing'); // constructors in derived classes must call super()
    }

    printMeeting(): void {
        console.log('The Accounting Department meets each Monday at 10am.');
    }

    generateReports(): void {
        console.log('Generating accounting reports...');
    }
}

let department: Department; // ok to create a reference to an abstract type
department = new Department(); // error: cannot create an instance of an abstract class
department = new AccountingDepartment(); // ok to create and assign a non-abstract subclass
department.printName();
department.printMeeting();
department.generateReports(); // error: method doesn't exist on declared abstract type

Interfaces

Interfaces (2)

Extending Interfaces

interface GridDefinition {
	origin : { x: number; y: number; };
	calculateDistanceFromOrigin( point: { x: number; y: number; })
}

//ERROR! 
class Grid implements GridDefinition{
    static origin = {x: 0, y: 0}; //The interface won't see static members
    calculateDistanceFromOrigin(point: {x: number; y: number;}) {
        let xDist = (point.x - Grid.origin.x);
        let yDist = (point.y - Grid.origin.y);
        return Math.sqrt(xDist * xDist + yDist * yDist) / this.scale;
    }
    constructor (public scale: number) { }
}

Interface with Static Properties

Generics

Generic Classes

function assign<T extends U, U>(target: T, source: U): T {
    for (let id in source) {
        target[id] = source[id];
    }
    return target;
}

let x = { a: 1, b: 2, c: 3, d: 4 };
assign(x, { b: 10, d: 20 }); // { a : 1, b: 10, c: 3, d: 20}
assign(x, { e: 0 });  // Error

Type parameters as constraints

F-Bounded Polymorphism