Utilize the class type of a method parameter as the method type for another parameter

Question

Utilize the class type of a method parameter as the method type for another parameter

Here's a quick example illustrating my desired functionality.

// Every time, the ACL class will have a different name such as "UsersACL", etc.
export class EventsACL {
    test(): { read: true, write: true } {
        
    }
}

// This function acts as a decorator for other methods
function ACL(obj: {
    aclClass: any,
    wantedProperties: aclClass.test
});


// Calling it
ACL({ acl: EventsACL, { read: true, write: false });

This means that if I modify the EventsACL test function, it should dynamically update the request value in wantedProperties. I prefer not to use predefined interfaces as I want this to be adaptable for any class.

typescript

Answer 1

Answer №1

If you're looking to achieve something similar, there's a technique you can use. The workaround we apply to determine the return type of test may seem unconventional, but rest assured that the method itself won't actually be invoked during runtime. You can experiment with this concept on the TypeScript playground:

var dummy = (false as true) && EventsACL.prototype.test();

is functionally valid because TypeScript's type checker assumes the function evaluation process, even though in JavaScript it simplifies to

var dummy = false && EventsACL.prototype.test();

, preventing actual execution at runtime.

export class EventsACL {
  test(): {
    read: boolean,
    write: boolean
  } {
    return {
      read: true, write: false
    }
  }
}

// `aclObj` in this context refers to any typed object featuring a `test` method — like an instance of EventsACL or UsersACL.
var dummy = (false as true) && aclObj.test();
type ReturnType = typeof dummy;

function ACL(obj: {
  aclClass: any,
  wantedProprties: ReturnType
}) {

}

ACL({
  aclClass: EventsACL,
  wantedProprties: {
    read: true,
    write: false
  }
});

Answer 2

If you're looking to achieve something similar, there's a technique you can use. The workaround we apply to determine the return type of test may seem unconventional, but rest assured that the method itself won't actually be invoked during runtime. You can experiment with this concept on the TypeScript playground:

var dummy = (false as true) && EventsACL.prototype.test();

is functionally valid because TypeScript's type checker assumes the function evaluation process, even though in JavaScript it simplifies to

var dummy = false && EventsACL.prototype.test();

, preventing actual execution at runtime.

export class EventsACL {
  test(): {
    read: boolean,
    write: boolean
  } {
    return {
      read: true, write: false
    }
  }
}

// `aclObj` in this context refers to any typed object featuring a `test` method — like an instance of EventsACL or UsersACL.
var dummy = (false as true) && aclObj.test();
type ReturnType = typeof dummy;

function ACL(obj: {
  aclClass: any,
  wantedProprties: ReturnType
}) {

}

ACL({
  aclClass: EventsACL,
  wantedProprties: {
    read: true,
    write: false
  }
});

Utilize the class type of a method parameter as the method type for another parameter

Answer №1

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