How can I define "custom method" type passed to constructor?

[low musk]

class foo {
  customAdd?: (foo: unknown) => this
  constructor(customAdd?: (foo: unknown) => this) { // A 'this' type is available only in a non-static member of a class or interface.
    this.customAdd = customAdd
  }
  add(foo: unknown): this {
    if (this.customAdd) {
      return this.customAdd(direction);
    }
    // default add
  }
}

foo have children classes, so this might refer to it's children but not itself, and I don't an as is a proper solution.

if I define it as (foo: unknown) => foo, this would happen:

class bar extends foo {}
new Bar(() => new bar()) // this throws, because () => bar is not assignable to () => foo

I need foo to be readonly, to make feature like history

I need Copying methods but not mutating methods

[low musk]

!helper

[mortal vault]

you need to use "this" parameter of functions

https://www.typescriptlang.org/docs/handbook/2/functions.html#declaring-this-in-a-function

[low musk]

sorry but just like I said before, this could change because there are children classes, Maybe I've understood something wrong, but asserting the type of this might not help as I need to assert it as (this: this)

[low musk]

Just like this case, new Bar(function(){ return new bar() }) will still throws, (this: foo)=> foo won't accept (this: bar) => bar

I need to define a type that is sultable for all children classes

[low musk]

if it accepts it will still throws some where as return type bar has been assumed to be foo

[low musk]

(this: this) => this sounds stupid, and it is indeed not feasible

But anyway, thank you for your help

!helper

[low musk]

!helper

[mortal vault]

oh you want it to work with inheritance

[low musk]

yes

[low musk]

If my title doesn't meet expectations, I can change it

[mortal vault]

i don't think that is possible, mostly due to this https://github.com/microsoft/TypeScript/issues/38038

my best suggestion is to not use inheritance here sorry u ran into this issue

[low musk]

i c, maybe the best way to do is define types for all children

thanks

!resolved

[slate fiber]

what's going on with this helper spam

3 times for the same post