How to get Categories and sub-categories in single API response-CodePudding

I have two collections Categories and Subcategories inside Categories colletion I have an array that is storing an ids of subcategories that are stored in Subcategories collection.Below is my document structure:

Categories collection

{
  id:65,
  title:"Automotive",
  active:true,
  subcategories:[35,28,30]
}

subcategories collection

{
  id:35,
  title:"Automotive technology",
  category_id:65,
  active:true
},
{
  id:28,
  title:"Automotive coatings",
  category_id:65,
  active:true
},
{
  id:30,
  title:"Machinery and equipments",
  category_id:65,
  active:true
}

AS seen in above collection 3 documents from subcategories collection have been associated with the category document. I want to fetch data in below format on single API hit.

API response should be in below format:

{
 data:{
     category:{
               id:65,
               title:"Automotive",
               subcategories:[{
                                id:35, 
                                name:"Automotive technology",
                              },
                              {
                                id:28, 
                                name:"Automotive coatings",
                              },
                              {
                                id:30, 
                                name:"Machinery and equipments",
                             }]
              },
     category:{
                 id:66,
                 title:"Food",
                 subcategories:[{
                                 id:23, 
                                 name:"Drinks",
                                },
                                {
                                 id:2, 
                                 name:"Additives",
                               }]
               },
   },
   messsage:"Success",
   code:200
}

AS of now I am able to get data in 2 api hits that is like first getting all the categories

 const category = await db.categories.find({});

Then on click of some particular category fetching all the sub categories based on the category id.

const subCategories = await db.SubCategories.find({category_id:id});

Someone let me know how can I get the above data in desired format in single API hit.Any help would be appreciated.

CodePudding user response：

You need something like this, also, if you use mongoose, you can use .populate()

To format data you can use $project stage in aggregation pipeline or projection in .find()

CodePudding user response：

#If u wanna use mongoose with populate:

CategorySchema:

const CategorySchema= new mongoose.Schema({
  ...
  subCategories: [{ type: Number, ref: 'SubCategory' }],
  ...
});

ref content is must be equal to model name like

module.exports = mongoose.model('SubCategory', SubCategorySchema);

Controller:

const categories = await Armature.find({})
  .populate({
    path: 'subCategories'
  })

path content is must be equal to column name

#If you wanna write with mongo query

db.getCollection("categories").aggregate([
    {
       $lookup:
         {
             from: 'subCategories',
             localField: 'subCategories',
             foreignField: 'id',
             as: 'subCategories'
         }
    }
])