Unique and custom validation decorator within NestJS, applicably used on the service layer

Question

Unique and custom validation decorator within NestJS, applicably used on the service layer

I am using a subscribe function in a nestjs service to receive rabbit messages.

  @RabbitSubscribe({
    exchange: 'test'.
    routingKey: 'test',
    queue: 'q'
  })
  async handleEvent( msg: msgModel) {
    console.log(message)
  }

I have multiple subscribers set up like this and I want to implement model validation similar to what we do in controllers with validationPipe()

However, the validationPipe() or guard does not work on a simple service.

Therefore, I am looking to create a custom decorator that can validate the message received.

Something along these lines:

  @CustomDec(msg)
  @RabbitSubscribe({
    exchange: 'test'.
    routingKey: 'test',
    queue: 'q'
  })
  async handleEvent( msg: msgModel) {
    console.log(message)
  }

or 
  @RabbitSubscribe({
    exchange: 'test'.
    routingKey: 'test',
    queue: 'q'
  })
  async handleEvent( @customDec() msg: msgModel) {
    console.log(message)
  }

Is it feasible to achieve this?

typescript rabbitmq decorator nestjs

Answer 1

Answer №1

To achieve this, you can utilize a method-decorator. Here is an example:

function MessageValidator(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
    const originalMethod = descriptor.value;
    descriptor.value = function (...args: any[]) {
        const messageModel = args[0];
        console.log("validating message...");
        if(messageModel.message === "isExpectedMessage") {
          console.log("OK")
        } else {
            console.log("NOK")
        }
        return originalMethod.apply(this, args);
    }
}

Implement it like so:

@RabbitSubscribe({
    exchange: 'test',
    routingKey: 'test',
    queue: 'q'
})
@MessageValidator
async handleEvent(message: messageModel) {
    console.log(message)
}

Check out the play on TypeScript playground.

Answer 2

To achieve this, you can utilize a method-decorator. Here is an example:

function MessageValidator(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
    const originalMethod = descriptor.value;
    descriptor.value = function (...args: any[]) {
        const messageModel = args[0];
        console.log("validating message...");
        if(messageModel.message === "isExpectedMessage") {
          console.log("OK")
        } else {
            console.log("NOK")
        }
        return originalMethod.apply(this, args);
    }
}

Implement it like so:

@RabbitSubscribe({
    exchange: 'test',
    routingKey: 'test',
    queue: 'q'
})
@MessageValidator
async handleEvent(message: messageModel) {
    console.log(message)
}

Check out the play on TypeScript playground.

Unique and custom validation decorator within NestJS, applicably used on the service layer

Answer №1

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