How to pass a generic type into an object property callback function

Question

I'm trying to pass a generic type to a callback lambda function

interface Interface { 
   onChange: <T = string>(val: T) => void 
}

const handleOnChange = (val: MY_ENUM) => {...}

const myConfig: Interface[] = [{
    onChange: <MY_ENUM>(val) => handleOnChange(val);
}]

the code above doesn't work.

I don't know why it is mandatory to put a comma after you provide a generic. — CodeNewbie, Feb 10 '22 at 13:11
This is because TS expect jsx syntax. With comma, TS is aware that you are writing generics — captain-yossarian from Ukraine, Feb 10 '22 at 13:12

score 0 · Answer 1 · answered Feb 10 '22 at 13:19

0

interface Interface {
  onChange: <T = string>(val: T) => void
}

const handleOnChange = <T,>(val: T) => { }

const myConfig: Interface[] = [{
  onChange: handleOnChange
}]

You had to add a COMMA at the beginning of your config function when passing the generic
Thanks to, @captain-yossarian

answered Feb 10 '22 at 13:19

CodeNewbie

173
1
10

2

you don't have to use comma, a simple `T extends any` will also work. – ABOS Feb 10 '22 at 13:23
Btw, take a look on [this](https://github.com/microsoft/TypeScript/pull/47607) PR, it will be possible to write `onChange: handleOnChange` – captain-yossarian from Ukraine Feb 10 '22 at 13:27

How to pass a generic type into an object property callback function

1 Answers1