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realtime data with GraphQL subscriptions / apollo-server

using Apollo server:




1. server.js


const {
ApolloServer,
gql,
AuthenticationError,
PubSub
} = require('apollo-server')

const pubsub = new PubSub()


const server = new ApolloServer({
typeDefs,
resolvers,
formatError: error => {
console.log(JSON.stringify(error))
return { ...error }
},

introspection: true,
playground: true,
context: async ({ req, connection }) => {
if (connection) {
return { pubsub }
}

if (req) {
const me = await getMe(req)

return {
me,
secret: process.env.SECRET,
pubsub
}
}
}
})


2. schema: project.js

extend type Subscription {
projectAdded: Project
}
3. resolver: project.js

const PROJECT_CHANNEL = 'PROJECT_CHANNEL'
Mutation: {
addProject: combineResolvers(
isAuthenticated,
async (parent, { projectInput }, { models, me, pubsub }) => {
const { projectName, clientId } = projectInput
const project = await Project.create({
accountId: me.accountId,
projectName: projectName || 'default project',
clientId: clientId || 0
})

console.log(me.accountId)
if (me.accountId === 'sat')
pubsub.publish('PROJECT_CHANNEL', { projectAdded: project })

return project
}
),
Subscription: {
projectAdded: {
subscribe: (parent, args, { pubsub }) => {
return pubsub.asyncIterator(PROJECT_CHANNEL)
}
}
}
4. front end App.js

const wsLink = new WebSocketLink({
uri: REACT_APP_WSURI,
options: {
reconnect: true
}
})
const uploadLink = createUploadLink({ uri: REACT_APP_GRAPHQL_URL })

const terminatingLink = split(
({ query }) => {
const { kind, operation } = getMainDefinition(query)
return kind === 'OperationDefinition' && operation === 'subscription'
},
wsLink,
uploadLink
)

const link = ApolloLink.from([authLink, terminatingLink])

5. Front end: dashboard.js

const { loading, error, data, refetch, subscribeToMore } = useQuery(
GET_PROJECTS
)

<ProjectList
styles={styles}
projects={projects}
navigation={navigation}
onRefresh={onRefresh}
refreshing={refreshing}
onEditProject={onEditProject}
onDeleteProject={onDeleteProject}
subscribeToNewProject={() =>
subscribeToMore({
document: ADD_PROJECT_SUBSCRIPTION,
variables: {},
updateQuery: (prev, { subscriptionData }) => {
if (!subscriptionData.data) return prev
const newProject = subscriptionData.data.projectAdded
console.log(newProject)
return Object.assign({}, prev, {
projects: [newProject, ...prev.projects]
})
}
})
}
/>

6.  project-list.js

componentDidMount () {
this.props.subscribeToNewProject()
}


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