Given the following typed React component using generic type arguments, how would I go about wrapping it in React's new forwardRef
API?
type Props<T> = {
forwardedRef?: Ref<HTMLInputElement>
...
}
class GenericComponent<T> extends Component<Props<T>> {
...
}
const ComponentWithRef = forwardRef<HTMLInputElement, Props<T>>((props, ref) => (
<StringInput<T> {...props} forwardedRef={ref} />
))
The above approach has no way to define the T
generic.
So, to broaden the question some, this is really a question about preserving generic types in higher order functions. The following usage of forwardRef
will properly typecheck (in 3.0.1
)
const SelectWithRef = forwardRef(<Option extends string>(props: Props<Option>, ref?: Ref<HTMLSelectElement>) =>
<Select<Option> {...props} forwardedRef={ref} />);
But, the Option
generic is immediately resolved to string
, rather than remaining as a generic. As such, the following does not typecheck
const onChange: (value: 'one' | 'two') => void = (value) => console.log(value);
<SelectWithRef<'one' | 'two'>
^^^^^^^^^^^^^^^ [ts] Expected 0 type arguments, but got 1
value="a"
options={['one', 'two']}
onChange={onChange}
^^^^^^^^^^ [ts] Type 'string' is not assignable to type '"one" | "two"'
/>
The relevant issue is tracked in this Typescript issue ticket.