moodhyalbannai/task-express-m5-relations-2-nosql

Express Relations

Setup

1. Create a MONGODB_URL variable in the .env file.
2. Install all requirements.
3. Inspect the projects models and api directory.
4. Read the task fully.
5. Import the Relations Course Task.postman_collection.json into Postman to help speed testing along.

Task

One-to-Many Relation

A course has many lectures. E.g. A course like React, has many lectures dedicated for many topics, like useState, react-query, react-router-dom. So we will try to create this type relationship by doing the following:

1. Setup
   • Create a course and a lecture using postman.
2. Create a relation between the Lecture model and the Course model:
   • In the db/models/Lecture.js add a property called course, where the type is a mongoose ObjectId that references the Course model
3. Create add a route and controller function that establishes a relation:
   • In the api/lectures Add a route with post as the method and /:lectureId as the url
   • Create a controller called addToCourse in the api/lectures/lectures.controllers.js file and export it.
   • In the controller, update the lecture found in the req.lecture by setting the course property to equal the course property in the req.body.
4. Now that we have a relationship in the lecture finished, we now need to add many lectures to the Course model:
   • In db/models/Course.js add a property called lectures, assign it and empty array.
   • Inside the empty array, add an object where the key called type is set to a mongoose ObjectId and the key ref references the Lecture model.
5. Back in the lecture controllers file:
   • Import the Course model.
   • Inside the addToCourse function, use the Course model and the findByIdAndUpdate query to find the course using the id in the request body, then push the lecture id to the the courses list of the tag.
   • return an empty response with the status set to 204.
6. Test your endpoint in postman:
   • Setup a request to use the endpoints you created earlier, and send JSON with the key of course set to a value of an id of a course that exists.
7. Lets populate the list of courses and the list of lectures.
   • In lectures.controllers.js, update the find method with populate to retrieve details on the course property. Test it in Postman using both adding a course to an existing lecture.
   • In the courses.controllers.js, update the find method with populate to retrieve details on the lectures property.

Many-to-Many Relation

A course can have many tags. E.g. A course like React, has many tags such as frontend, javascript, library. And a tag can have many courses, e.g. a tag of frontend can have css, html, javascript, react as associated courses.So we will try to create this type relationship by doing the following:

1. Setup
   • Create a course and a tag using postman.
2. Create a relation between the Course model and the Tag model:
   • In db/models/Course.js add a property called tags, assign it and empty array.
   • Inside the empty array, add an object where the key called type is set to a mongoose ObjectId and the key ref references the Tag model.
3. Create a relation between the Tag model and the Course model:
   • In db/models/Tag.js add a property called courses, assign it and empty array.
   • Inside the empty array, add an object where the key called type is set to a mongoose ObjectId and the key ref references the Course model.
4. Create add a route and controller function that establishes a relation:
   • In the api/courses Add a route with post as the method and /:courseId as the url.
   • Create a controller called addTagToCourse in the api/courses/courses.controllers.js file and export it.
   • In the controller, update the course found in the req.course by setting pushing the req.body.tag into the tags property of the req.course.
   • Import the Tag model into the courses.controllers.js.
   • Inside the addTagToCourse function, use the Tag model and the findByIdAndUpdate query to find the tag using the id in the request body, then push the course id of the course to the the courses list of the tag.
   • return an empty response with the status set to 204.
5. Test your endpoints in postman:
   • Setup a request to use the endpoint you created earlier, and send JSON with the key of tag set to a value of an id of a tag that exists.
6. Lets populate the list of courses and the list of tags.
   • In tags.controllers.js, update the find method with populate to retrieve details on the courses property.
   • In the courses.controllers.js, update the find method by chaining an extra populate to retrieve details on the tags property.
   • Test it in Postman using both adding an existing tag to a course.

Bonus

One-to-Many Relation Bonus

1. When populating the list of lectures in the courses.controllers.js, only select the id and the name of the lecture.
2. When populating the list of a lectures for details of the course, only select the course name.
3. Update the createLecture and the updateLectureById in the lectures.controller to add a relation to the course if it was in the req.body.
4. Modify the deleteLectureById to remove a lecture id from the course list when a lecture is deleted.

Many-to-Many Relation Bonus

1. When populating the list of courses in the courses.controllers.js, only select the id and the name of the tags.
2. When populating the list of a tags only select the course name.
3. Update the createCourse and the updateCourseById in the lectures.controller to add a relations to the tags if it was in the req.body, try doing this is a list of tags.
4. Modify the deleteCourseById to remove a course id from the tags the course has relations with when after a course gets deleted.