CODEWITHSUNDEEP
typescriptclassinheritancetypescript-typings
Kyle.Tryon
Kyle.Tryon

Reputation: 54

Typescript type of class which extends a known class

I am modeling a data structure in code to create an SDK. I have for example, two "types" of "letter" available. The abstract class letter states that a character property will always be present.

Further down there will be a function that will take in the letter and print the character. The issue is, each class that extends letter is its own type. How could this function expect to take in any class which extends letter?

abstract class Letter {
  abstract character: string
}

class A extends Letter {
  character = "A"
}

class B extends Letter {
  character = "B"
}

function printLetter(letter: Letter) {
  console.log(letter.character)
}

printLetter(A) // see error

Error:

Argument of type 'typeof A' is not assignable to parameter of type 'Letter'.
  Property 'character' is missing in type 'typeof A' but required in type 'Letter'.(2345)

Upvotes: 0

Views: 112

Answers (1)

Oleksandr Kovalenko
Oleksandr Kovalenko

Reputation: 616

abstract class Letter {
  abstract character: string
}

class A extends Letter {
  character = "A"
}

class B extends Letter {
  character = "B"
}

function printLetter(letter: Letter) {
  console.log(letter.character)
}

const aInstance = new A()

printLetter(aInstance)

Upvotes: 1

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