Decorators : Retrieving Parent of a Class in Argument

[night relic]

Hello folks!

I am building a library using proposal-decorators

I want to retrieve the parent of a class in argument

Could someone help ?

https://www.typescriptlang.org/play/?#code/GYVwdgxgLglg9mABAGzgczQUwE4AoLICGAzsQILZoBciAYuNPGAJSIDeAUIt4hAsXGSYAdKjS4uPKQRLlKwsIQC2mADSSp3APRbEAchmkKaYQAdC2TGCh7EGxMw4BfDhy0Aqd13eJMAD1NMaEwAExoAIjJw1UQwBEwtcBDMYBgwUK1w8O8tDgABMSxsDkNiRDJ2FzdPb18AoKhQiIAhaMRI7MR3XIL0IpKiUkRmusawELKKtiqPLy66wOCw9oBhNvDWnPzCnAHZRBXRqwnhyo4gA

[mint pendant]

@night relic Here's a shortened URL of your playground link! You can remove the full link from your message.

malix_off#0

Playground Link

Preview:```ts
function logger(classArg: Function) {
console.log(
classArg.name,
// 'classArg.parent'
)
}

/**

• expected: "A", none/undefined/""
  */
  @logger
  class A {}

/**

• expected: "B", "A"
  */
  @logger
  class B extends A {}

/**

• expected: "C", "B"
  ...```

You can choose specific lines to embed by selecting them before copying the link.

[onyx oracle]

I have no idea about all this, but I found this: https://stackoverflow.com/questions/43912168/typescript-decorators-with-inheritance

which seems to solve this problem

[swift siren]

@night relic Object.getPrototypeOf(classArg).name

[night relic]

Thanks for this link, will dig into it !

[night relic]

And thanks for this snippet, it worked 👍

[night relic]

Do you know why Object.getPrototypeOf(classArg).name is not the same as classArg.prototype.name ?

[swift siren]

prototype gets the prototype of the current object

Err, probably not saying that right. If you do User.prototype that's the prototype for User objects.

class User {}
User.prototype.name = "Bob";

new User().name; // "Bob"

(Not valid TS code but this is how the JS works)

[night relic]

I still don't grasp their difference enough, I think

[timber wasp]

I think User.prototype is the prototype of a User instance

Object.getPrototypeOf is the prototype of the current object

class Thing {}
class User extends Thing {}
const userInstance = new User

User.prototype === Object.getPrototypeOf(userInstance)
Object.getPrototypeOf(User) === Thing

[swift siren]

@night relic If you really want to get into the nitty-gritty of how inheritance works in JS, you may want to read up on it with something like https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain

But the core part is that each object (potentially) has a backwards link to a prototype that it shares state with:

JavaScript implements inheritance by using objects. Each object has an internal link to another object called its prototype. That prototype object has a prototype of its own, and so on until an object is reached with null as its prototype.
This backwards link is what Object.getPrototypeOf(x) returns. It's also available as x.__proto__ but this syntax isn't preferred (it was originally a non-standard syntax)