I'm trying to write a generic React component that requires props of one of two types (IFoo
or IBar
) and a component that accepts props of the selected type.
How come the following doesn't work?
import React from 'react';
interface IFoo {
x: string;
}
interface IBar {
x: number;
}
const foo: React.FunctionComponent<IFoo> = (props: IFoo) => {
console.log("hello from foo!");
return <div>foo</div>
};
const bar: React.FunctionComponent<IBar> = (props: IBar) => {
console.log("hello from bar!");
return <div>bar</div>
};
interface IProps<T> {
props: T[];
Component: React.FunctionComponent<T>;
}
class HigherOrderComponent<T extends IBar | IFoo> extends React.Component<IProps<T>> {
render() {
const { props, Component } = this.props;
return (<div>
{props.map(prop => <Component {...prop}/>)};
</div>)
}
}
This returns the following error:
Type 'T' is not assignable to type 'IntrinsicAttributes & T & { children?: ReactNode; }'.
Type 'IFoo | IBar' is not assignable to type 'IntrinsicAttributes & T & { children?: ReactNode; }'.
Type 'IFoo' is not assignable to type 'IntrinsicAttributes & T & { children?: ReactNode; }'.
Type 'IFoo' is not assignable to type 'T'.
'IFoo' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'IFoo | IBar'.
Type 'T' is not assignable to type 'IntrinsicAttributes'.
Type 'IFoo | IBar' is not assignable to type 'IntrinsicAttributes'.
Type 'IFoo' has no properties in common with type 'IntrinsicAttributes'.(2322)
Quick fix is to add:
{props.map((prop: T & {}) => <Component {...prop}/>)};
I think the problem is with the spread operator and union type (if there is only one type it works fine). I know TS had problems with that before :(
Hope this helps :)