Exploring the functionality of decorators for Configuration and Route Mapping in TypeScript and Loopback4

When working with Loopback4 REST Endpoints/Operations, such as "GET /greet," they are configured using a Decorator above the method that handles the query and returns the desired result:

 @get('/greet', spec)
  greet(name: string) {return "hello"}

As someone who is new to both Loopback and Typescript, I am curious about how these configuration Decorators function in a broader context (including other frameworks).

Here are some more specific questions I have:

  • Are the decorators processed during the build phase, resulting in generated configuration code? Or are they only processed at runtime?
  • If processing occurs at runtime, how does a decorator containing pre-configuration information work before it can even be triggered when the method is called? Is there a TypeScript function that retrieves an Array of all applied Decorators?
  • ...

Thank you for your help!

Answer №1

During the build process, these elements are assessed and necessitate the inclusion of the experimentalDecorators: true setting in the tsconfig.json file to activate them.

For a comprehensive understanding of decorators, check out the TypeScript documentation provided at: https://www.typescriptlang.org/docs/handbook/decorators.html

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