CODEWITHSUNDEEP
graphqlaws-amplify
GBMR
GBMR

Reputation: 604

How to create a one to many relationship using GraphQL?

I have an iOS app where users can login and message one another using the backend AWS Amplify. My API is configured using GraphQL and currently looks like this.

type User @model {
  id: ID!
  userSub: String!
  fullName: String!
}
type ChatMessage @model {
  id: ID!
  senderUserSub: String
  recieverUserSub: String
  messageText: String
  messageImageFilename: String
  dateSent: String!
}

I am new to GraphQL and its Schema Definition Language. The schema above works however inside the dynamodb table there is no structure to it, I am trying to create an efficient way of structuring data for user messaging. The "One to many relationship" is schema example that can be found inside of the Amplify CLI when configuring an API. I try to copy its example base my current one off of.

Default one to many relationship schema

type Blog @model {
  id: ID!
  name: String!
  posts: [Post] @connection(keyName: "byBlog", fields: ["id"])
}

type Post @model @key(name: "byBlog", fields: ["blogID"]) {
  id: ID!
  title: String!
  blogID: ID!
  blog: Blog @connection(fields: ["blogID"])
  comments: [Comment] @connection(keyName: "byPost", fields: ["id"])
}

type Comment @model @key(name: "byPost", fields: ["postID", "content"]) {
  id: ID!
  postID: ID!
  post: Post @connection(fields: ["postID"])
  content: String!
}

I try to copy its example like this.

Updated schema

type User @model {
  id: ID!
  userSub: String!
  fullName: String!
  messages: [ChatMessage] @connection(keyName: "byUser", fields: ["id"])
}
type ChatMessage @model @key(name: "byUser", fields: ["messageID"]){
  id: ID!
  messageID: ID!
  senderUserSub: String
  recieverUserSub: String
  messageText: String
  messageImageFilename: String
  dateSent: String!
  user: User @connection(fields: ["messageID"])
}

I was wondering does this updated schema above even look appropriate? If possible can anyone give me pointers as to how to make one correctly for messaging? I am not experienced when it comes to GraphQL SDL.

Upvotes: 2

Views: 5457

Answers (1)

Engam
Engam

Reputation: 1061

You don't need to use the @key attribute for this kind of connection. You can give the @connection a name so that amplify understands which connection you are referring to like this:

@connection(name: "nameOfYourConnection")

The name must be provided on the connection attribute on both types.

type User @model {
  id: ID!
  userSub: String
  fullName: String
  chatMessages: [ChatMessage] @connection(name: "UserChatMessageConnection") #new
}

type ChatMessage @model {
  id: ID!
  senderUserSub: String 
  recieverUserSub: String
  messageText: String
  messageImageFilename: String
  dateSent: String!
  user: User @connection(name: "UserChatMessageConnection") #new
}

After you have run amplify push you will se in the generated mutations, that when you are creating a ChatMessage object you should give it a value named chatMessagesUserId. This is the reference (the id on the user type) to which user created the ChatMessage.

Upvotes: 5

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