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Quick Start Guide

Quick Overview of Typegoose​

note

This Guide is for Typegoose version ~12.0

Typegoose is a "wrapper" for easily writing Mongoose models with TypeScript.

Instead of writing this:

// This is a representation of how typegoose's compile output would look
interface Car {
  model?: string;
}

interface Job {
  title?: string;
  position?: string;
}

interface User {
  name?: string;
  age!: number;
  preferences?: string[];
  mainJob?: Job;
  jobs?: Job[];
  mainCar?: Car | string;
  cars?: (Car | string)[];
}

const JobSchema = new mongoose.Schema({
  title: String;
  position: String;
});

const CarModel = mongoose.model('Car', {
  model: String,
});

const UserModel = mongoose.model('User', {
  name: { type: String },
  age: { type: Number, required: true },
  preferences: [{ type: String }],
  mainJob: { type: JobSchema },
  jobs: [{ type: JobSchema }],
  mainCar: { type: Schema.Types.ObjectId, ref: 'Car' },
  cars: [{ type: Schema.Types.ObjectId, ref: 'Car' }],
});

You can just write this:

class Job {
  @prop()
  public title?: string;

  @prop()
  public position?: string;
}

class Car {
  @prop()
  public model?: string;
}

class User {
  @prop()
  public name?: string;

  @prop({ required: true })
  public age!: number; // This is a single Primitive

  @prop({ type: () => [String] })
  public preferences?: string[]; // This is a Primitive Array

  @prop()
  public mainJob?: Job; // This is a single SubDocument

  @prop({ type: () => [Job] })
  public jobs?: Job[]; // This is a SubDocument Array

  @prop({ ref: () => Car })
  public mainCar?: Ref<Car>; // This is a single Reference

  @prop({ ref: () => Car })
  public cars?: Ref<Car>[]; // This is a Reference Array
}
caution

type has to be defined when working with Arrays, because Reflection only returns basic information. Look here for why
Like public: string[] is in reflection only Array.

Look here for what ! means on a property
Look here for what ? means on a property

How to Start using typegoose​

Requirements​

  • TypeScript version ^5.3 is recommended, though older ones may also work
  • NodeJS >=16.20.1 (and @types/node@16)
  • Mongoose ~8.9.0
  • A IDE that supports TypeScript linting is recommended to be used (VSCode is recommended)
  • This Guide expects you to know how Mongoose (or at least its models) works
  • experimentalDecorators and emitDecoratorMetadata must be enabled in tsconfig.json
  • tsconfig option target being at least es6, recommended is es2020
info

tsconfig option emitDecoratorMetadata is not strictly required, look here for more

Install​

npm install --save @typegoose/typegoose # install typegoose itself

npm install --save mongoose # install peer-dependency mongoose

How to use Typegoose​

Let's say you have a Mongoose model like this one:

const kittenSchema = new mongoose.Schema({
  name: String
});

const KittenModel = mongoose.model('Kitten', kittenSchema);

let document = await KittenModel.create({ name: 'Kitty' });
// "document" has basic mongoose inferred types

With Typegoose, it can be converted to something like:

class KittenClass {
  @prop()
  public name?: string;
}

const KittenModel = getModelForClass(KittenClass);

let document = await KittenModel.create({ name: 'Kitty' });
// "document" has proper (manual) typescript types of KittenClass
note

new KittenModel({} /*<-- this here*/) will have type suggestions, but they are not enforced, read more here.

note

Since around mongoose 6.0, mongoose can infer types mostly from the schema definition, but it is still not perfect and arguably less overview-able than typegoose's style of classes.
Also tsdoc comments are not transferred when using mongoose's inferred types.

Do's and Don'ts of Typegoose​

  • Typegoose is a wrapper for Mongoose's models & schemas
  • Typegoose does not modify any functions of Mongoose
  • Typegoose aims to get Mongoose's models to be stable through type-information from classes (without defining extra interfaces)
  • Typegoose aims to make Mongoose more usable by making the models more type-rich with TypeScript
  • Decorated schema configuration classes (like KittenClass above) must use explicit type declarations

Extra Examples​

Static Methods​

Sometimes extra functions for model creation or pre-written queries are needed, they can be done as follows:

class KittenClass {
  @prop()
  public name?: string;

  @prop()
  public species?: string;

  // the "this" definition is required to have the correct types
  public static async findBySpecies(this: ReturnModelType<typeof KittenClass>, species: string) {
    return this.find({ species }).exec();
  }
}
const KittenModel = getModelForClass(KittenClass);

const docs = await KittenModel.findBySpecies('SomeSpecies');
note

pre-6.0 static functions needed @staticMethod, but this is not needed anymore.

Instance Methods​

Sometimes extra functions for manipulating data on an instance are needed, they can be done as follows:

class KittenClass {
  @prop()
  public name?: string;

  @prop()
  public species?: string;

  // the "this" definition is required to have the correct types
  public async setSpeciesAndSave(this: DocumentType<KittenClass>, species: string) {
    this.species = species;
    await this.save();
  }
}
const KittenModel = getModelForClass(KittenClass);

const doc = new KittenModel({ name: 'SomeCat', species: 'SomeSpecies' });
await doc.setSpeciesAndSave('SomeOtherSpecies');
note

Pre-6.0 static functions needed @instanceMethod, but this is not needed anymore.

Hooks​

Typegoose also supports hooks. They can be used like this:

@pre<KittenClass>('save', function() {
  this.isKitten = this.age < 1
})
@post<KittenClass>('save', function(kitten) {
  console.log(kitten.isKitten ? 'We have a kitten here.' : 'We have a big kitty here.')
})
class KittenClass {
  @prop()
  public name?: string;

  @prop()
  public species?: string;
  
  @prop()
  public age?: number
  
  @prop({ default: false })
  public isKitten?: boolean
}

const KittenModel = getModelForClass(KittenClass);

const doc = new KittenModel({ name: 'SomeCat', species: 'SomeSpecies', age: 0 });
await doc.save(); // this should output "We have a kitten here."
const doc = new KittenModel({ name: 'SomeCat', species: 'SomeSpecies', age: 2 });
await doc.save(); // this should output "We have a big kitty here."

For detailed explanation of Hooks, please see Hooks.

Note:

  • Do not use Arrow Functions, because it will break the binding of this
  • For ESLint users: Make sure that rule eslint-no-use-before-defining is disabled, otherwise you might get ESLint errors / warnings inside the hooks