How to chain two GraphQL queries in sequence using Apollo Client

问题

I am using Apollo Client for the frontend and Graphcool for the backend. There are two queries firstQuery and secondQuery that I want them to be called in sequence when the page opens. Here is the sample code (the definition of TestPage component is not listed here):

export default compose(
        graphql(firstQuery, {
            name: 'firstQuery'
        }),
        graphql(secondQuery, { 
            name: 'secondQuery' ,
            options: (ownProps) => ({
                variables: {
                   var1: *getValueFromFirstQuery*
                }
            })
        })
)(withRouter(TestPage))

I need to get var1 in secondQuery from the result of firstQuery. How can I do that with Apollo Client and compose? Or is there any other way to do it? Thanks in advance.

回答1:

The props added by your firstQuery component will be available to the component below (inside) it, so you can do something like:

export default compose(
  graphql(firstQuery, {
    name: 'firstQuery'
  }),
  graphql(secondQuery, { 
    name: 'secondQuery',
    skip: ({ firstQuery }) => !firstQuery.data,
    options: ({firstQuery}) => ({
      variables: {
          var1: firstQuery.data.someQuery.someValue
      }
    })
  })
)(withRouter(TestPage))

Notice that we use skip to skip the second query unless we actually have data from the first query to work with.

Using the Query Component

If you're using the Query component, you can also utilize the skip property, although you also have the option to return something else (like null or a loading indicator) inside the first render props function:

<Query query={firstQuery}>
  {({ data: { someQuery: { someValue } = {} } = {} }) => (
    <Query
      query={secondQuery}
      variables={{var1: someValue}}
      skip={someValue === undefined}
    >
      {({ data: secondQueryData }) => (
        // your component here
      )}
</Query>

Using the useQuery Hook

You can also use skip with the useQuery hook:

const { data: { someQuery: { someValue } = {} } = {} } = useQuery(firstQuery)
const variables = { var1: someValue }
const skip = someValue === undefined
const { data: secondQueryData } = useQuery(secondQuery, { variables, skip })

Mutations

Unlike queries, mutations involve specifically calling a function in order to trigger the request. This function returns a Promise that will resolve with the results of the mutation. That means, when working with mutations, you can simply chain the resulting Promises:

const [doA] = useMutation(MUTATION_A)
const [doB] = useMutation(MUTATION_B)

// elsewhere
const { data: { someValue } } = await doA()
const { data: { someResult } } = await doB({ variables: { someValue } })

回答2:

For anyone using react apollo hooks the same approach works.

You can use two useQuery hooks and pass in the result of the first query into the skip option of the second,

example code:

const AlertToolbar = ({ alertUid }: AlertToolbarProps) => {
  const authenticationToken = useSelectAuthenticationToken()

  const { data: data1 } = useQuery<DataResponse>(query, {
    skip: !authenticationToken,
    variables: {
      alertUid,
    },
    context: makeContext(authenticationToken),
  })

  const { data: data2, error: error2 } = useQuery<DataResponse2>(query2, {
    skip:
      !authenticationToken ||
      !data1 ||
      !data1.alertOverview ||
      !data1.alertOverview.deviceId,
    variables: {
      deviceId:
        data1 && data1.alertOverview ? data1.alertOverview.deviceId : null,
    },
    context: makeContext(authenticationToken),
  })

  if (error2 || !data2 || !data2.deviceById || !data2.deviceById.id) {
    return null
  }
  const { deviceById: device } = data2
  return (
    <Toolbar>
    ...
    // do some stuff here with data12

来源：https://stackoverflow.com/questions/49317582/how-to-chain-two-graphql-queries-in-sequence-using-apollo-client

标签

graphql

apollo

react-apollo

apollo-client

graphcool