AWS AppSync Amplify 与 Transformer v2 的关系 - 无法检索相关类型数据答案

【问题标题】：AWS AppSync Amplify Relationship with Transformer v2 - Can't Retrieve related type dataAWS AppSync Amplify 与 Transformer v2 的关系 - 无法检索相关类型数据
【发布时间】：2022-10-16 20:19:51
【问题描述】：

所以我目前正在使用 AWS AppSync 和 Amplify，一切都很好，除了使用新的 Transformer V2，我很难让事情正常工作。

这是我的架构：

type Post
  @model
  @auth(
    rules: [
      { allow: owner, ownerField: "username" }
      { allow: public, operations: [read] }
    ]
  ) {
  id: ID!
  title: String!
  content: String!
  username: String
    @index(name: "postsByUsername", queryField: "postsByUsername")
  coverImage: String
  comments: [Comment] @hasMany
 
}


type Comment
  @model
  @auth(
    rules: [
      { allow: owner, ownerField: "createdBy" }
      { allow: public, operations: [read] }
    ]
  ) {
  id: ID!
  message: String
  
}

我可以创建帖子和评论。但是，每当我查询帖子列表时，我从来没有得到 cmets。

下面是一个查询示例：

query MyQuery {
  listPosts {
    items {
      comments {
        items {
          id
          message
          createdAt
        }
      }
      content
      title
      username
    }
  }
}

这是我得到的相应结果：

{
  "data": {
    "listPosts": {
      "items": [
        {
          "comments": {
            "items": []
          },
          "content": "Testing stuff",
          "title": "Today is the day",
          "username": "bawp"
        },
        {
          "comments": {
            "items": []
          },
          "content": "### hello\n````\n function call()\n```",
          "title": "next item of the day",
          "username": "paulod"
        },
        {
          "comments": {
            "items": []
          },
          "content": "Hello Word",
          "title": "santo dia",
          "username": "paulod"
        }
      ]
    }
  }
}

注意如何

     "comments": {
            "items": []
          },

它总是空的！

尽管如此，当我查询 Comments 表时，我至少添加了一条评论。

query MyQuery {
  listComments {
    items {
      id
      message
      createdBy
    }
  }
}

结果：

{
  "data": {
    "listComments": {
      "items": [
        {
          "id": "ddddf58b-df1c-498c-97b4-6d61361b4b9e",
          "message": "Thjis is may coment here\n\n```\nCode could go here also!\n```",
          "createdBy": "paulod"
        }
      ]
    }
  }
}

我不确定我在这里缺少什么。请记住，我使用的是新指令（Transformer v2），而不是旧的关系指令，例如

@connection

任何帮助是极大的赞赏。

非常感谢！

【问题讨论】：

标签： amazon-web-services relationship amplify

【解决方案1】：

好的，这是对可能遇到其中一些问题的任何人的问题的回应。

首先，

架构！由于我在表之间添加了一些关系，因此必须正确添加指令。以下是我对架构所做的更改：

type Post
  @model
  @auth(
    rules: [
      { allow: owner, ownerField: "username" }
      { allow: public, operations: [read] }
    ]
  ) {
  id: ID!
  title: String!
  content: String!
  username: String
    @index(name: "postsByUsername", queryField: "postsByUsername")
  coverImage: String
  comments: [Comment] @hasMany(indexName: "byPost", fields: ["id"]) #check out: https://docs.amplify.aws/cli/graphql/data-modeling/#has-many-relationship
}

#Comment
#queries: null - removes any authorization rules for queries, allowing anyone to query for comments
#ownerField:createdBy - sets the createdBy field as the currently signed in user
type Comment
  @model
  @auth(
    rules: [
      { allow: owner, ownerField: "createdBy" }
      { allow: public, operations: [read] }
    ]
  ) {
  id: ID!
  message: String
  post: Post @belongsTo(fields: ["postID"])
  postID: ID @index(name: "byPost")
 
}

接下来，因为 appsync 在每次推送时都会自动生成 queries.js 文件，所以我不得不手动编辑这个文件（这并不是真正的最终解决方案）。特别是 listPosts 查询：

export const listPosts = /* GraphQL */ `
  query ListPosts(
    $filter: ModelPostFilterInput
    $limit: Int
    $nextToken: String
  ) {
    listPosts(filter: $filter, limit: $limit, nextToken: $nextToken) {
      items {
        id
        title
        content
        username
        coverImage
        comments {
          items {
            id
            message
            postID
            createdAt
            updatedAt
            createdBy
          }
        }
        createdAt
        updatedAt
      }
      nextToken
    }
  }
`;

你看，当这个文件被自动生成时，它会有“nextToken”而不是我想要查询的字段。换句话说，comments 字段将具有 { nextToken }

因此，查询将如下所示：

export const listPosts = /* GraphQL */ `
  query ListPosts(
    $filter: ModelPostFilterInput
    $limit: Int
    $nextToken: String
  ) {
    listPosts(filter: $filter, limit: $limit, nextToken: $nextToken) {
      items {
        id
        title
        content
        username
        coverImage
        comments {
          nextToken # --> this is what was autogenerated, which was giving me issues!!!
        }
        createdAt
        updatedAt
      }
      nextToken
    }
  }
`;

一旦我将nextToke 更改为我在帖子前面向您展示的内容，一切都完美无缺。

现在，我知道手动更改此文件似乎不对。但是，我还没有找到更好的方法来做到这一点。

但就目前而言，这就是我能想到的。

我希望这可以帮助遇到类似问题的人。

谢谢！

【讨论】：

【解决方案2】：

我已经像您在答案中一样应用了架构，但也使 postId 字段很重要。

我认为这有助于获得嵌套的 cmets。

type Post
  @model
  @auth(
    rules: [
      { allow: owner, ownerField: "username" }
      { allow: public, operations: [read] }
      { allow: private, operations: [read] }
    ]
  ) {
  id: ID!
  title: String!
  content: String!
  username: String
    @index(name: "postsByUsername", queryField: "postsByUsername")
  coverImage: String
  comments: [Comment] @hasMany(indexName: "byPost", fields: ["id"]) #check out: https://docs.amplify.aws/cli/graphql/data-modeling/#has-many-relationship
}

#Comment
#queries: null - removes any authorization rules for queries, allowing anyone to query for comments
#ownerField:createdBy - sets the createdBy field as the currently signed in user
type Comment
  @model
  @auth(
    rules: [
      { allow: owner, ownerField: "createdBy" }
      { allow: public, operations: [read] }
      { allow: private, operations: [read] }
    ]
  ) {
  id: ID!
  message: String
  post: Post @belongsTo(fields: ["postID"])
  postID: ID! @index(name: "byPost")
}

【讨论】：