How to create a generic arrow function with react and typescript

Question

I'm trying to create a generic wrapper component for apollo graphql results. I want this wrapper to wait for the query to complete successfully then render a component that was passed into the props. The passed in component should have props of type QueryResult<T>.

This code snippet gives me an error on Col 66 saying

Cannot find name 'T'.ts(2304)

import React from 'react';
import { QueryResult } from 'react-apollo';
import { useSandboxContext } from 'src/js/shared/components/SandboxContext';
import { ErrorContent } from 'src/js/shared/components/ErrorContent';
import { PageSpinner } from 'src/js/shared/components/PageSpinner';

interface WrapperComponentProps<T> extends QueryResult<T> {
  // TODO: figure out how to specify that the wrapped component takes the results
  // Something like this `React.ReactType<QueryResult<T>>` but this causes errors
  wrappedComponent: React.ReactType;
}

// Getting an error from `React.FC<WrapperComponentProps<T>>`
// `Cannot find name 'T'.ts(2304)`
export const ApolloResultWrapper: React.FC<WrapperComponentProps<T>> = <T extends object>(props: WrapperComponentProps<T>) => {
  const sandbox = useSandboxContext();

  if (props.error) {
    sandbox.logger.error('query failed', props.error);

    return <ErrorContent />
  }
  if (props.loading) {
    return <PageSpinner />;
  }

  if (!props.data) {
    return <ErrorContent />
  }

  // TODO: figure out how to spread all the props except wrappedComponent
  return <props.wrappedComponent {...props} wrappedComponent={undefined} />;
}

Swazimodo · Accepted Answer · 2020-05-22 14:17:15Z

Finally managed to solve the issue

interface WrappedComponentProps<T> {
  data: T
}

interface WrapperComponentProps<T, K> {
  apolloResult: QueryResult<T>;
  wrappedComponent: React.ComponentType<WrappedComponentProps<T> & K>;
  componentProps: Omit<K, keyof WrappedComponentProps<T>>;
}

type ComponentProps<T, K> = React.PropsWithChildren<WrapperComponentProps<T, K>>;

export const ApolloResultWrapper = <T extends object, K = {}>(props: ComponentProps<T, K>) => {
  const sandbox = useSandboxContext();

  if (props.apolloResult.error) {
    sandbox.logger.error('stuff broke', props.apolloResult.error);

    return <ErrorContent />
  }
  if (props.apolloResult.loading) {
    return <PageSpinner />;
  }
  if (!props.apolloResult.data) {
    return <ErrorContent />
  }

  return <props.wrappedComponent
    children={props.children}
    data={props.apolloResult.data}
    {...props.componentProps as K}
  />;
}

vicacid · Accepted Answer · 2020-05-13 16:13:42Z

0

If the error is about <T extends object> place try to change type casting <T extends object> to .... as T extends object

https://www.typescriptlang.org/docs/handbook/jsx.html#the-as-operator

answered May 13, 2020 at 16:13

vicacid

5574 silver badges6 bronze badges

1 Comment

Swazimodo Over a year ago

Thanks for your suggestion. I have added comments into my code snippet which will make it easier to see the errors I'm having.

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