Populate method is not working as expected

Question

I have 2 schemas project and task.

const mongoose = require("mongoose"); 
const projectSchema = new mongoose.Schema({
  title: String,
  sub_title: String,
  tasks: [{ type: mongoose.Schema.Types.ObjectId, ref: "Task" }],
});

const Project = mongoose.model("Project", projectSchema);

module.exports = Project;

const mongoose = require("mongoose"); 
const taskSchema = new mongoose.Schema({
  title: String,
  sub_title: String,
  time: String,
  projectId: String,
  timeSheet:[],
  project: { type: mongoose.Schema.Types.ObjectId, ref: "Project" },
});

const Task = mongoose.model("Task", taskSchema);

module.exports = Task;

I let the user enter the project details and then can add the tasks in it. I used populate method to get the all tasks related to a specific project inside of project schema . But when I get all projects it is not adding tasks in it. Please help me with this bug.

I have tried to add tasks by pushing it but when I update the task it is not showing in projects schema

Answer 1

Unfortunately, mongoose relations are not established automatically and therefore you will still need to add the Project _id into each Task. Just like you have added each Task _id into the project array of each Project.

//Get the id of the Project and Task that are related
const projectid = req.body.projectid;
const taskid = req.body.taskid;

// Get the Parent Project. I have used findById() for demonstration 
const project = await Project.findById(projectid);

// Add the project._id ObjectId into the task.project field. 
// I have used findByIdAndUpdate() for demonstration 
const task = await Task.findByIdAndUpdate(taskid,
   { project: project._id },
   { new: true }
);

// Add the task._id ObjectId into the project.tasks array.  
project.tasks.push(task._id);
await project.save();

Now when you want to get the Projects and call populate it will lookup the Tasks and replace the ObjectId with the full document in each Project.