What about combining a fat arrow function with a nested decorator?

Trying to implement a fat arrow function with a nestjs decorator in a controller.

Can it be done in the following way :

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

When attempting this, TypeScript throws an error message:

Unable to resolve signature of property decorator when called as an expression
, indicating that it does not work as expected.

Preference lies on using fat arrow functions over the traditional function declaration:

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

Hence the query about the feasibility of the first approach.

Answer №1

The answer is negative, primarily due to the differences between an arrow function and a traditional function in JavaScript. Arrow functions alter the lexical context of this and do not have access to arguments. For more detailed information on this distinction, refer to this explanation.

Moreover, using arrow functions can limit the utilization of class functions, hindering the ability to work with instances of services.

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

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

The above code snippet successfully retrieves the string returned by appService.sayHello(). However, if written as follows:

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

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

the code would fail to return the desired string from appService.sayHello() due to the absence of reference to appService.

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