Node.js - 如何使用 graphql 获取关联的模型数据？

Posted 2023-03-08

【中文标题】Node.js - 如何使用 graphql 获取关联的模型数据？

【英文标题】：Node.js - How to get associated model data using graphql?

【发布时间】：2021-11-27 10:49:29

【问题描述】：

在 Node.js 应用程序中，我使用 graphql 来获取数据列表。我创建了两个模型，称为School 和Grade。像 School 这样的模型的关联有很多 Grades 并且 Grade 属于 School。 查询时，我得到 null 关联模型的值。

在模型 school.js 中，

module.exports = (sequelize, Sequelize) => 
 const School = sequelize.define("school", 
  name: 
   type: Sequelize.STRING,
  ,
  email: 
    type: Sequelize.STRING,
  ,
 );

 School.associate = function (models) 
  School.hasMany(models.Grade,  foreignKey: "school_id" );
 ;

 return School;
;

在 typeDefs.graphql 中，

type Query 
  getSchoolDetails: [School]
  getSchoolDetail(id: ID!): School
  getGradeDetails: [Grade]


type School 
  id: ID!
  name: String
  email: String
  grades: [Grade]


type Grade 
  id: ID!
  school_id: ID!
  name: String
  school: School

在 resolvers.js 中，

const Query = 
 getSchoolDetails: async () => 
  try 
    const schools = await school.findAll();
    return schools;
   catch (err) 
    console.log(err);
  
 ,
 getSchoolDetail: async (root,  id ) => 
  try 
    const scl = await school.findByPk(id);
    return scl;
   catch (err) 
    console.log(err);
  
 ,
 getGradeDetails: async () => 
  try 
    const grades = await grade.findAll();
    return grades;
   catch (err) 
    console.log(err);
  
 ,

当我在操场上查询时，

query 
 getSchoolDetails
  id
  name
  email
  grades
    name
  
 

输出是，

 "data": 
   "getSchoolDetails": [
    
      "id": "1",
      "name": "Rotary West School",
      "email": "[e-mail]",
      "grades": null
    ,
    
      "id": "2",
      "name": "Excel Public School",
      "email": "[e-mail]",
      "grades": null
    ,
  ]

当我查询以获取成绩时，以与 null 相同的方式上学。我正在学习nodejs与graphql的关系，请帮我解决这个问题。

【参考方案1】：

您必须在 resolvers.js 文件中使用包含查询，如下所示

getSchoolDetails: async () => 
                try 
                    const schools = await school.findAll(
                        include: [ model: Grade ],
                    );
                    return schools;
                 catch (err) 
                    console.log(err);
                
            ,

这将获得与学校相关的所有成绩

如果你想include school with grade you have to associate grade with school using Grades belongsTo school