Fat arrow function and nest's decorator?

Question

I am trying to use fat arrow function with a nestjs decorator in a controller.

So is it possible to do something like this :

@Controller()
export class AppController {
  @Get()
  findAll = (): string  => 'This is coming from a fat arrow !';
}

With this code typescript is telling me this : Unable to resolve signature of property decorator when called as an expression so it isn't working.

I prefer to use fat arrow function instead of this "traditional" function :

@Controller()
export class AppController {
  @Get()
  findAll(): string {
    return 'This is not comming from a fat arrow';
  }
}

This is why I am asking if something like this a possible.

Answer 1

I would say the answer is no, for the very reason of how the arrow function differs from a function in JavaScript, namely changing the lexical this and arguments. This answer goes into a lot of detail about how function () {} differs from myFunction = () => {}.

Along with that, using arrow functions would disallow a lot of using class functions, so if you are injecting any instances of a service, you would not be able to use them.

@Injectable()
export class AppController {
  constructor (private readonly appService: AppService) {}

  @Get('/')
  hello(): string {
    return this.appService.sayHello();
  }
}

Would work and return the string from the appService.sayHello() function, but this

@Injectable()
export class AppController {
  constructor (private readonly appService: AppService) {}

  @Get('/')
  hello = (): string => {
    return this.appService.sayHello();
  }
}

would not return the string from the appService.sayHello() function because it does not know about the appService.