Added state pattern example

Author: Savjee

state/state.ts

@@ -0,0 +1,124 @@
+module test {
+
+    interface State {
+        order: Order;
+
+        cancelOrder();
+        verifyPayment();
+        shipOrder();
+    }
+
+    class Order {
+        public cancelledOrderState: State;
+        public paymentPendingState: State;
+        public orderShipedState: State;
+        public orderBeingPrepared: State;
+
+        public currentState: State;
+
+        constructor() {
+            this.cancelledOrderState = new CancelledOrderState(this);
+            this.paymentPendingState = new PaymentPendingState(this);
+            this.orderShipedState = new OrderShippedState(this);
+            this.orderBeingPrepared = new OrderBeingPrepared(this);
+
+            this.setState(this.paymentPendingState);
+        }
+
+        public setState(state: State) {
+            this.currentState = state;
+        }
+
+        public getCurrentState(): State{
+            return this.currentState;
+        }
+    }
+
+    class CancelledOrderState implements State {
+        order: Order;
+
+        constructor(order: Order) {
+            this.order = order;
+        }
+
+        public cancelOrder() {
+            console.log('This order is already cancelled');
+            this.order.setState(this.order.cancelledOrderState);
+        }
+
+        public verifyPayment() {
+            console.log('The order is cancelled, you cannot pay anymore.');
+        }
+
+        public shipOrder() {
+            console.log('The order is cancelled, you cannot ship it anymore.');
+        }
+    }
+
+    class PaymentPendingState implements State {
+        order: Order;
+
+        constructor(order: Order) {
+            this.order = order;
+        }
+
+        cancelOrder() {
+            console.log('Cancelling your unpaid order...');
+            this.order.setState(this.order.cancelledOrderState);
+        }
+
+        verifyPayment() {
+            console.log('Payment verified! Shipping soon.');
+            this.order.setState(this.order.orderBeingPrepared);
+        }
+        shipOrder() {
+            console.log('Cannot ship order when payment is pending!');
+        }
+    }
+
+    class OrderBeingPrepared implements State {
+        order: Order;
+
+        constructor(order: Order) {
+            this.order = order;
+        }
+
+        cancelOrder() {
+            console.log('Cancelling your order.. You will be refunded.');
+            this.order.setState(this.order.cancelledOrderState);
+        }
+        verifyPayment() {
+            console.log('Payment is already verified.');
+        }
+        shipOrder() {
+            console.log('Shipping your order now..');
+            this.order.setState(this.order.orderShipedState);
+        }
+    }
+
+    class OrderShippedState implements State {
+        order: Order;
+
+        constructor(order: Order) {
+            this.order = order;
+        }
+
+        cancelOrder() {
+            console.log('You cannot cancel an order that has been shipped.');
+        }
+        verifyPayment() {
+            console.log('Payment is already verified');
+        }
+        shipOrder() {
+            console.log('Order is already shipped');
+        }
+    }
+
+    let order = new Order();
+
+    order.getCurrentState().verifyPayment();
+    order.getCurrentState().shipOrder();
+    order.getCurrentState().cancelOrder();
+
+    console.log('Order state: ' + (<any> order.getCurrentState()).constructor.name);
+}