How does Query.prototype.cast() work in Mongoose ?
The Query.prototype.cast() function casts this query to the schema of the model. And if the obj is present, then it is casted instead of this query.
Syntax:
Query.prototype.cast()
Parameters: This function has one parameter i.e. the model to cast and if not set, then the default is this.model.
Return Value: This function returns Query Object.
Installing mongoose :
npm install mongoose
After installing the mongoose module, you can check your mongoose version in command prompt using the command.
npm mongoose --version
After that, you can just create a folder and add a file for example, index.js as shown below.
Example 1:
index.js
const mongoose = require( 'mongoose' ); // Database connection mongoose.connect( 'mongodb://127.0.0.1:27017/w3wiki' , { useNewUrlParser: true , useCreateIndex: true , useUnifiedTopology: true }); // User model const User = mongoose.model( 'User' , { name: { type: String }, age: { type: Number } }); const query = User.find() var res = query.cast(); console.log( "Casted to self:" , res) |
The project structure will look like this:
Run index.js file using below command:
node index.js
Output:
Casted to self: {}
Example 2:
index.js
const express = require( 'express' ); const mongoose = require( 'mongoose' ); const app = express() // Database connection mongoose.connect( 'mongodb://127.0.0.1:27017/w3wiki' , { useNewUrlParser: true , useCreateIndex: true , useUnifiedTopology: true }); // User model const User = mongoose.model( 'User' , { name: { type: String }, age: { type: Number } }); const query = User.find() var res = query.cast(); console.log( "Self Casting:" , res) app.listen(3000, function (error ){ if (error) console.log(error) console.log( "Server listening on PORT 3000" ) }) |
The project structure will look like this:
Run index.js file using below command:
node index.js
Output:
Server listening on PORT 3000 Self Casting: {}
Reference: https://mongoosejs.com/docs/api/query.html#query_Query-cast
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