我对 GraphQl 相当陌生,我在这里遵循了 GraphQL NodeJS 后端教程:GraphQL Realtime Subscriptions。一切正常,我完成了教程。接下来,我在这里学习了带有 Apollo 前端的 VueJS 教程:Vue & Apollo Subscriptions。我选择使用我在第一个教程中创建的 GraphQL 服务器,而不是使用前端教程中使用的 GraphCool。这是我卡住的部分。如果我打电话
subscription {
Link(filter: {
mutation_in: [CREATED]
}) {
node {
id
url
description
}
}
}
在 GraphiQL 客户端中,我确实得到了id
,url
并且description
当我在不同的浏览器选项卡中使用数据创建新链接时
data: Link: node: {id: "59ef0bbeef32bb05692ee4b4", url: "http://new-test-url2.com", description: "Test description2"}
(此订阅调用也在后端教程中进行)。但是当我打电话
subscription {
Link(filter: {
mutation_in: [CREATED]
}) {
node {
id
url
description
postedBy {
id
name
}
votes {
id
user {
id
}
}
}
}
}
我得到错误:
{message: "Cannot destructure property `Users` of 'undefined' or 'null'.",…}
{message: "Cannot destructure property `Votes` of 'undefined' or 'null'.",…}
与数据data:{Link: {node: null}}
我只是找不到这个问题的答案。希望有人可以帮助我这个。这是我的代码:
架构/index.js
type Link {
id: ID!
url: String!
description: String!
postedBy: User
votes: [Vote!]!
}
type User {
id: ID!
name: String!
email: String!
password: String!
votes: [Vote!]!
}
type Vote {
id: ID!
user: User!
link: Link!
}
type SigninPayload {
token: String
user: User
}
type Query {
allLinks(filter: LinkFilter, skip: Int, first: Int): [Link!]!
}
type Mutation {
createLink(url: String!, description: String!): Link
createVote(linkId: ID!): Vote
createUser(name: String!, email: String!, password: String!): User
signinUser(email: String!, password: String!): SigninPayload!
}
type Subscription {
Link(filter: LinkSubscriptionFilter): LinkSubscriptionPayload
Vote(filter: VoteSubscriptionFilter): VoteSubscriptionPayload
}
input LinkSubscriptionFilter {
mutation_in: [_ModelMutationType!]
}
input VoteSubscriptionFilter {
mutation_in: [_ModelMutationType!]
}
type LinkSubscriptionPayload {
mutation: _ModelMutationType!
node: Link
}
type VoteSubscriptionPayload {
mutation: _ModelMutationType!
node: Vote
}
input LinkFilter {
OR: [LinkFilter!]
description_contains: String
url_contains: String
}
enum _ModelMutationType {
CREATED
UPDATED
DELETED
}
架构/resolvers.js:
Query: {
allLinks: async (root, {filter, first, skip}, {mongo: {Links, Users}}) => {
let query = filter ? {$or: buildFilters(filter)} : {};
const cursor = Links.find(query);
if (first) {
cursor.limit(first);
}
if (skip) {
cursor.skip(skip);
}
return cursor.toArray();
},
},
Mutation: {
createLink: async (root, data, {mongo: {Links}, user}) => {
assertValidLink(data);
const newLink = Object.assign({postedById: user && user._id}, data);
const response = await Links.insert(newLink);
newLink.id = response.insertedIds[0];
pubsub.publish('Link', {Link: {mutation: 'CREATED', node: newLink}});
return newLink;
},
createUser: async (root, data, {mongo: {Users}}) => {
const newUser = {
name: data.name,
email: data.email,
password: data.password,
};
const response = await Users.insert(newUser);
return Object.assign({id: response.insertedIds[0]}, newUser);
},
createVote: async (root, data, {mongo: {Votes}, user}) => {
const newVote = {
userId: user && user._id,
linkId: new ObjectID(data.linkId),
};
const response = await Votes.insert(newVote);
return Object.assign({id: response.insertedIds[0]}, newVote);
},
signinUser: async (root, data, {mongo: {Users}}) => {
const user = await Users.findOne({email: data.email});
if (data.password === user.password) {
return { token: `token-${user.email}`, user };
}
},
},
Subscription: {
Link: {
subscribe: () => pubsub.asyncIterator('Link'),
},
},
Link: {
id: root => root._id || root.id,
// postedBy: async ({postedById}, data, {dataloaders: {userLoader}}) => {
// return await userLoader.load(postedById);
// },
postedBy: async ({postedById}, data, {mongo: {Users}}) => {
return await Users.findOne({_id: postedById});
},
votes: async ({_id}, data, {mongo: {Votes}}) => {
return await Votes.find({linkId: _id}).toArray();
},
},