Logger in functional component

[slow anvil]

Hello,

I've a Custom Middleware in Nestjs which I've written in Functional Middleware, but unfortunately I am not able to use Logger & don't have any idea that how to use Logger in that from @nestjs/common .

can anyone help me how to use Logger from @nestjs/common in Functional Middleware?

[limpid monolith]

seems to me that you need a dependecy there and if so a functional middleware is not what you need here

i think you can achieve that with a class based middleware

[slow anvil]

Yes, I can achieve the Logger using Class based middleware, but that that class based middleware can't be used in main.ts with app.use() for Global Middleware

[limpid monolith]

so why you need a logger there?

[limpid monolith]

what exactly are you trying to log?

[slow anvil]

instead of console.log I am using logger

[limpid monolith]

ok and what are you trying to log?

[slow anvil]

throw new BadRequestException(Missing query params for ${req.path}: ${missingParams.join(", ")});

this I want to log as well

[limpid monolith]

i think that should be at the controller isnt?

if i were you i would do it at the controller so i do the validation at the controller in the specific route i need it for

[slow anvil]

Yup, but I don't want to repeat the Code, I am trying DRY, so doing this way, that's why I am checking for Logger in Functional Middleware, as I've achieved the Logger properly in class based middleware...

[limpid monolith]

can you show me the code of how you are doing it

[slow anvil]

for Class based??

[outer adder]

You can do manual dependency injection with function based middleware - instead of just the middleware, create a function that takes logger as an argumen, and returns the middleware function as a closure with the logger.

Then, in main, retrieve the logger from DI and pass it like so

app.use(getMiddleware(logger))

But, if you use Nest's logger abstraction, you don't need to use DI, you can just call new Logger(name) and use that. The loogger is gobal and proxies call to any custom logger configured with app.useLogger

[slow anvil]

Sorry but I didn't get you here

[outer adder]

function getMiddleware(logger: Logger) {
  return (req, res, next) => {
    // do stuff
    logger.log(stuff)
    return next()
  }
}

[limpid monolith]

so you would have to instantiate the logger at the app file and then send the instance of this logger on the middleware correct?

if so maybe this would be more clear for him