Dealing with circular dependencies in mongoose: Strategies and solutions

Question

Dealing with circular dependencies in mongoose: Strategies and solutions

I am working on a code snippet for my application

const citySchema = new Schema({
cityName: {
    type: String,
    required: true,
  },
  citizen:[{
      type: Schema.Types.ObjectId,
      ref: "Citizen",
  }],
});
module.exports = mongoose.model("City", citySchema);


const citizenSchema = new Schema({
  citizenName: {
    type: String,
    required: true,
  },
  city:{
      type: Schema.Types.ObjectId,
      ref: "City",
  },
});

module.exports = mongoose.model("Citizen", citizenSchema);

router.post('/', (req, res) => {
      // req.body.cityName
      // req.body.citizenName
})

When making a POST request, I receive both the city name (for a new city) and citizen name (for a new citizen) that are not already in the database. However, I want to ensure that both these schemas are updated correctly by:

Ensuring City contains references to Citizens
Ensuring Citizen contains reference to the City

How can I achieve this? Your assistance would be much appreciated.

javascript express mongoose mongoose-schema

Answer 1

Answer №1

Instead of following that approach, I highly recommend utilizing referencing through pre-hook middleware in your data model for a more efficient process.

Your code should resemble the following:

const citySchema = new Schema({
cityName: {
    type: String,
    required: true,
  },
  citizen:[{
      type: Schema.Types.ObjectId,
      ref: "Citizen",
  }],
});

// Query middleware to populate the 'citizen' attribute whenever the 'find' function is invoked.
citySchema.pre(/^find/, function (next) {
  this.populate('citizen');
  next();
});

module.exports = mongoose.model("City", citySchema);

const citizenSchema = new Schema({
  citizenName: {
    type: String,
    required: true,
  },
  city:{
      type: Schema.Types.ObjectId,
      ref: "City",
  },
});

citizenSchema.pre(/^find/, function (next) {
  this.populate('city');
  next();
});

module.exports = mongoose.model("Citizen", citizenSchema);

If you wish to only select the ID and not the complete data, an example implementation could be as follows:

citizenSchema.pre(/^find/, function (next) {
  this.populate({
    path: 'city',
    select: '_id',
  });
  next();
});

Explanation:

By incorporating this method, every time Mongoose functions like findByIdAndUpdate, find, findOne are executed, the referenced data will be displayed in the city and citizen attributes. This proves to be more efficient rather than updating each time new data is introduced.
The populate function serves to populate the attributes with data from another data model.
The object within the populate method specifies the model's 'name' (in the path) and determines which data to extract from the referenced model. In this instance, only the _id attribute is selected.

Answer 2

Instead of following that approach, I highly recommend utilizing referencing through pre-hook middleware in your data model for a more efficient process.

Your code should resemble the following:

const citySchema = new Schema({
cityName: {
    type: String,
    required: true,
  },
  citizen:[{
      type: Schema.Types.ObjectId,
      ref: "Citizen",
  }],
});

// Query middleware to populate the 'citizen' attribute whenever the 'find' function is invoked.
citySchema.pre(/^find/, function (next) {
  this.populate('citizen');
  next();
});

module.exports = mongoose.model("City", citySchema);

const citizenSchema = new Schema({
  citizenName: {
    type: String,
    required: true,
  },
  city:{
      type: Schema.Types.ObjectId,
      ref: "City",
  },
});

citizenSchema.pre(/^find/, function (next) {
  this.populate('city');
  next();
});

module.exports = mongoose.model("Citizen", citizenSchema);

If you wish to only select the ID and not the complete data, an example implementation could be as follows:

citizenSchema.pre(/^find/, function (next) {
  this.populate({
    path: 'city',
    select: '_id',
  });
  next();
});

Explanation:

By incorporating this method, every time Mongoose functions like findByIdAndUpdate, find, findOne are executed, the referenced data will be displayed in the city and citizen attributes. This proves to be more efficient rather than updating each time new data is introduced.
The populate function serves to populate the attributes with data from another data model.
The object within the populate method specifies the model's 'name' (in the path) and determines which data to extract from the referenced model. In this instance, only the _id attribute is selected.

Dealing with circular dependencies in mongoose: Strategies and solutions

Answer №1

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