I have two models in my graphql schema and the one I am trying to query on, Sessions, has two #belongsTo directives (read on a forum this matters). I can successfully save these models and view them on the AWS AppSync Queries Tab where I can query getSessions successfully BUT when I try to the exact same query locally following these docs:
(https://docs.amplify.aws/lib/graphqlapi/advanced-workflows/q/platform/flutter/#combining-multiple-operations)
I get an error locally:
type "Null" is not a subtype of type 'string'
What am I doing wrong and how do I fix this so I can successfully retrieve my nested query:
Here are my models as a reference:
Sessions:
type Session
#model
#auth(
rules: [
{ allow: public }
{ allow: owner }
{ allow: groups, groups: ["Admin"] }
]
) {
id: ID!
name: String
numPeoplePresent: Int
notes: String
eIdReader: String
weighTiming: String
cows: [Cow] #manyToMany(relationName: "CowSession")
proceduresID: ID
procedures: Procedures #hasOne(fields: ["proceduresID"])
}
Cow:
type Cow
#model
#auth(
rules: [
{ allow: public }
{ allow: owner }
{ allow: groups, groups: ["Admin"] }
]
) {
id: ID!
name: String!
RfId: String
weight: [Float!]!
temperament: [Int]
breed: String
type: String
dateOfBirth: AWSDate
sessions: [Session] #manyToMany(relationName: "CowSession")
procedures: [Procedures] #manyToMany(relationName: "CowProcedures")
}
This is the query that is causing the error:
const getSession = 'getSession';
String graphQLDocument = '''query getSession(\$id: ID!) {
$getSession(id: \$id) {
numPeoplePresent
notes
name
eIdReader
id
owner
proceduresID
updatedAt
weighTiming
cows {
items {
cow {
RfId
}
}
}
}
}''';
final getSessionRequest = GraphQLRequest<Session>(
document: graphQLDocument,
modelType: Session.classType,
variables: <String, String>{'id': sessID}, //parameter of the current session can hardcode to whatever you need here
decodePath: getSession,
);
final response =
await Amplify.API.query(request: getSessionRequest).response;
print('Response: ${response.data}');
The wonderful people at amplify answered this quickly so I will relay the information here:
the problem was the intermediary ids were not included in my local query so it was unable to retrieve the nested Cows. Updated query looks like this:
getSession = 'getSession';
String graphQLDocument = '''query getSession(\$id: ID!) {
$getSession(id: \$id) {
numPeoplePresent
notes
name
eIdReader
id
owner
proceduresID
updatedAt
weighTiming
cows {
items {
id <-- needed this one
cow {
id <-- and this id too
RfId
breed
dateOfBirth
name
type
weight
}
}
}
}
}''';
Related
From GraphQL Client's perspective, how do I perform a query with multiple nested resolvers where the fields from the parent are passed as arguments to the child resolver?
Here is a minimal example:
GraphQL Schema:
type Author {
id: ID!
name: String!
}
type Book {
id: ID!
title: String!
releaseDate: String!
}
type Query {
// Returns a list of Authors ordered by name, 'first' indicates how many entries to return
getAllAuthors(first: Int!): [Author]!
// Returns a list of Books ordered by releaseDate, 'first' indicates how many entries to return
getBooksByAuthorId(first: Int! authorId: ID!): [Book]!
}
Is it possible to write a query to get all authors and their last released book? Something around the lines:
query GetAuthorsWithLastBook($first: Int!) {
getAllAuthors(first: $first) {
authorId: id
name
lastBook: getBooksByAuthor(1, authorId) {
title
}
}
}
In the example above, I attempted to alias getAllAuthors.id as authorId and pass the alias down as argument to getBooksByAuthor(...) but that didn't work.
The key aspect of the problem is that I don't know the authorIds beforehand. I could fetch the authors first and build a query to fetch their last book but that will result in multiple queries and that is something I would like to avoid.
Update
A Java Kickstarter example is available here: https://www.graphql-java-kickstart.com/tools/schema-definition/
yes, on the graphql definition, you need to add lastBook in the Author
type Author {
id: ID!
name: String!
lastBook: [Book]
}
Next up u need to write the resolver for the lastBook
const resolvers = {
Query: {
Author {
lastBook: (parent, args) {
const userId = parent.id;
return getBooksByAuthor(userId, 1);
},
}
}
};
Maybe the title is not accurate but I really don't know how to describe it anymore. I went through multiple documentations and descriptions but still couldn't figure it out.
I want to implement a basic social media like followers/following query on my type User. I am using MySQL and for that I made a separate table called Follow as it's a many-to-many connection.
Here is a pseudo-ish representation of my tables in the database without the unnecessary columns:
Table - User
user_id primary key Int
Table - Follow
follow_er foreign_key -> User(user_id) Int
follow_ed foreign_key -> User(user_id) Int
A user could "act" as a follow_er so I can get the followed people
And a user could be follow_ed, so I can get the followers.
My prisma schema look like this:
model User {
user_id Int #id #default(autoincrement())
following Follow[] #relation("follower")
followed Follow[] #relation("followed")
}
model Follow {
follow_er Int
follower User #relation("follower", fields: [follow_er], references: [user_id])
follow_ed Int
followed User #relation("followed", fields: [follow_ed], references: [user_id])
##id([follow_er, follow_ed])
##map("follow")
}
By implementing this I can get the followers and following object attached to the root query of the user:
const resolvers = {
Query: {
user: async (parent, arg, ctx) => {
const data = await ctx.user.findUnique({
where: {
user_id: arg.id
},
include: {
following: true,
followed:true
}
})
return data
}....
Here is my GraphQL schema I tried to make:
type Query{
user(id: Int!): User
}
type User{
id: ID
following: [User]
followed: [User]
}
So I can get something like:
query {
user(id: $id) {
id
following {
id
}
followed{
id
}
}
}
}
But I couldn't make it work as even if I get the the array of objects of {follow-connections}:
[
{
follow_er:1,
follow_ed:2
},
{
follow_er:1,
follow_ed:3
},
{
follow_er:3,
follow_ed:1
},
]
I can't iterate through the array. As far as I know, I have to pass either the follow_er or follow_ed, which is a user_id to get a User object.
What am I missing? Maybe I try to solve it from a wrong direction. If anybody could help me with this, or just tell me some keywords or concepts I have to look for it would be cool. Thanks!
I would suggest creating self-relations for this structure in the following format:
model User {
id Int #id #default(autoincrement())
name String?
followedBy User[] #relation("UserFollows", references: [id])
following User[] #relation("UserFollows", references: [id])
}
And then querying as follows:
await prisma.user.findUnique({
where: { id: 1 },
include: { followedBy: true, following: true },
})
So you will get a response like this:
I am trying to understand graphql's query and mutation syntax. Given this example:
type Author {
id: Int!
firstName: String
lastName: String
posts: [Post]
}
type Post {
id: Int!
title: String
author: Author
votes: Int
}
type Query {
posts: [Post]
author(id: Int!): Author
}
What should the queries look like to associate a post with the author? Is this where connections come into play or is that something else? Here is my attempt at trying to solve the problem but to avail.
mutation createAuthor {
createAuthor(input: {
id: 123
firstName: "Bob"
lastName: "Smith"
}) {
id
firstName
lastName
}
}
query listAuthors {
listAuthors {
items {
id
firstName
lastName
}
}
}
mutation createPost {
createPost(input: {
id: 12345
title: "Title"
votes: 345
author: {
lastName: {
contains: "Bob"
}
}
}) {
id
title
votes
author {
id
firstName
lastName
}
}
}
Any help on this would be appreciated. My Goal is to Query an author and return all of the post's associated with that author as well as create a Post Mutation that adds a post to an author.
There are 2 questions in one, so I'll answer in the order there were asked.
1. return all of the posts associated with an author
Your schema looks correct. The query would look like:
query {
author(id: 1) {
id
posts {
id
title
}
}
}
2. create Post and attach to an author
In your example if you want to expose an interface to create a Post, then you would have to expose a mutation field in your schema
e.g:
type Mutation {
createPost(input: CreatePostInput): Post
}
if you want at the same time of creating a post, to also attach it to an author then you could add the authorId as part of the input, here we only want to attach the Post to an existing Author:
input CreatePostInput {
title: String
authorId: ID!
votes: Int
}
of course this is only the interface definition. We need to actually create the Post and link it to the Author inside the resolver.
The mutation query will look like:
mutation createPost {
createPost(input: {
title: "Title"
votes: 345
authorId: "authorId1"
}) {
id
title
votes
author {
id
firstName
lastName
}
}
}
Hope that helps!
Say I have the following GraphQL Schema
query {
allAuthors: [Author]
}
type Author {
id: ID!
name: String!
books: [Book]
}
type Book {
id: ID!
name: String!
author: Author!
}
Now I can successfully run the following query to get all the authors and their associated books
query {
allAuthors {
name,
books {
name
}
}
}
However, if I only want to get the first three books for all authors, how would I go about doing something like that? Can we index the books field in the Author type from within a query? If so, how?
I tried something like this and it doesn't work
query {
allAuthors {
name,
books[3] {
name
}
}
}
GraphQL doesn't have syntax for this.
You can add a "limit" parameter to a field, and this is common enough:
type Query {
allAuthors(limit: Int, offset: Int): [Author!]!
}
type Author {
id: ID!
name: String!
books(limit: Int, offset: Int): [Book!]!
}
If you add parameters like this to the schema, then the query you want (for all authors, get the first three books) could look like
{
allAuthors {
name
books(limit: 3) {
name
}
}
}
Given a GraphQL schema and resolvers for Apollo Server, and a GraphQL query, is there a way to create a collection of all requested fields (in an Object or a Map) in the resolver function?
For a simple query, it's easy to recreate this collection from the info argument of the resolver.
Given a schema:
type User {
id: Int!
username: String!
roles: [Role!]!
}
type Role {
id: Int!
name: String!
description: String
}
schema {
query: Query
}
type Query {
getUser(id: Int!): User!
}
and a resolver:
Query: {
getUser: (root, args, context, info) => {
console.log(infoParser(info))
return db.Users.findOne({ id: args.id })
}
}
with a simple recursive infoParser function like this:
function infoParser (info) {
const fields = {}
info.fieldNodes.forEach(node => {
parseSelectionSet(node.selectionSet.selections, fields)
})
return fields
}
function parseSelectionSet (selections, fields) {
selections.forEach(selection => {
const name = selection.name.value
fields[name] = selection.selectionSet
? parseSelectionSet(selection.selectionSet.selections, {})
: true
})
return fields
}
The following query results in this log:
{
getUser(id: 1) {
id
username
roles {
name
}
}
}
=> { id: true, username: true, roles: { name: true } }
Things get pretty ugly pretty soon, for example when you use fragments in the query:
fragment UserInfo on User {
id
username
roles {
name
}
}
{
getUser(id: 1) {
...UserInfo
username
roles {
description
}
}
}
GraphQL engine correctly ignores duplicates, (deeply) merges etc. queried fields on execution, but it is not reflected in the info argument. When you add unions and inline fragments it just gets hairier.
Is there a way to construct a collection of all fields requested in a query, taking in account advanced querying capabilities of GraphQL?
Info about the info argument can be found on the Apollo docs site and in the graphql-js Github repo.
I know it has been a while but in case anyone ends up here, there is an npm package called graphql-list-fields by Jake Pusareti that does this. It handles fragments and skip and include directives.
you can also check the code here.