如何跳过“useLazyLoadQuery”中的请求

Question

如何在useLazyLoadQuery中跳过请求/查询。

import { useLazyLoadQuery } from 'react-relay/hooks';

const id = props.selectedId // id can be a number or null
const user = useLazyLoadQuery(query, {id}) // skip query/request network if id is null

Answer 1

您可以使用@skip or @include directive。如果查询在指令条件下为空，则不会发出网络请求。考虑一下这个例子：

import { useLazyLoadQuery } from 'react-relay/hooks';

function MaybeUser(props) {
  const { userId } = props;
  //         is optional/nullable

  useLazyLoadQuery(
    graphql`
      query MaybeUserQuery($userId: ID!, $skip: Boolean!) {
        user(id: $userId) @skip(if: $skip) {
          fullName
        }
      }
    `,
    {
      userId: userId || '', // we need to pass something because of the query $userId type decleration
      skip: !userId,        // skip when there is no user ID
    },
  );

  return <magic />;
}

空userId生成一个空的MaybeUserQuery，导致没有网络请求。