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November 20, 2024 22:12
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An example implementation of a simple message bus in TypeScript using the publish-subscribe pattern
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| type MessageHandler = (message: any) => void; | |
| class MessageBus { | |
| private subscribers: Map<string, MessageHandler[]> = new Map(); | |
| // Subscribe to a specific message type | |
| subscribe(messageType: string, handler: MessageHandler): void { | |
| if (!this.subscribers.has(messageType)) { | |
| this.subscribers.set(messageType, []); | |
| } | |
| this.subscribers.get(messageType)!.push(handler); | |
| } | |
| // Unsubscribe a specific handler from a message type | |
| unsubscribe(messageType: string, handler: MessageHandler): void { | |
| const handlers = this.subscribers.get(messageType); | |
| if (handlers) { | |
| this.subscribers.set( | |
| messageType, | |
| handlers.filter((h) => h !== handler) | |
| ); | |
| } | |
| } | |
| // Publish a message of a specific type | |
| publish(messageType: string, message: any): void { | |
| const handlers = this.subscribers.get(messageType); | |
| if (handlers) { | |
| handlers.forEach((handler) => handler(message)); | |
| } | |
| } | |
| } | |
| // Usage example | |
| const messageBus = new MessageBus(); | |
| // Subscriber 1 | |
| messageBus.subscribe("orderPlaced", (message) => { | |
| console.log("Inventory Service: Order received:", message); | |
| }); | |
| // Subscriber 2 | |
| messageBus.subscribe("orderPlaced", (message) => { | |
| console.log("Notification Service: Sending confirmation for:", message); | |
| }); | |
| // Publish an event | |
| messageBus.publish("orderPlaced", { orderId: 123, product: "Laptop", quantity: 1 }); | |
| // Another example: Unsubscribe a handler | |
| const shippingHandler = (message: any) => { | |
| console.log("Shipping Service: Preparing package for:", message); | |
| }; | |
| messageBus.subscribe("orderPlaced", shippingHandler); | |
| messageBus.publish("orderPlaced", { orderId: 124, product: "Phone", quantity: 2 }); | |
| // Unsubscribe the shipping handler | |
| messageBus.unsubscribe("orderPlaced", shippingHandler); | |
| // Test after unsubscribing | |
| messageBus.publish("orderPlaced", { orderId: 125, product: "Tablet", quantity: 3 }); |
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