- 1. API with NestJS #1. Controllers, routing and the module structure
- 2. API with NestJS #2. Setting up a PostgreSQL database with TypeORM
- 3. API with NestJS #3. Authenticating users with bcrypt, Passport, JWT, and cookies
- 4. API with NestJS #4. Error handling and data validation
- 5. API with NestJS #5. Serializing the response with interceptors
- 6. API with NestJS #6. Looking into dependency injection and modules
- 7. API with NestJS #7. Creating relationships with Postgres and TypeORM
- 8. API with NestJS #8. Writing unit tests
- 9. API with NestJS #9. Testing services and controllers with integration tests
- 10. API with NestJS #10. Uploading public files to Amazon S3
- 11. API with NestJS #11. Managing private files with Amazon S3
- 12. API with NestJS #12. Introduction to Elasticsearch
- 13. API with NestJS #13. Implementing refresh tokens using JWT
- 14. API with NestJS #14. Improving performance of our Postgres database with indexes
- 15. API with NestJS #15. Defining transactions with PostgreSQL and TypeORM
- 16. API with NestJS #16. Using the array data type with PostgreSQL and TypeORM
- 17. API with NestJS #17. Offset and keyset pagination with PostgreSQL and TypeORM
- 18. API with NestJS #18. Exploring the idea of microservices
- 19. API with NestJS #19. Using RabbitMQ to communicate with microservices
- 20. API with NestJS #20. Communicating with microservices using the gRPC framework
- 21. API with NestJS #21. An introduction to CQRS
- 22. API with NestJS #22. Storing JSON with PostgreSQL and TypeORM
- 23. API with NestJS #23. Implementing in-memory cache to increase the performance
- 24. API with NestJS #24. Cache with Redis. Running the app in a Node.js cluster
- 25. API with NestJS #25. Sending scheduled emails with cron and Nodemailer
- 26. API with NestJS #26. Real-time chat with WebSockets
- 27. API with NestJS #27. Introduction to GraphQL. Queries, mutations, and authentication
- 28. API with NestJS #28. Dealing in the N + 1 problem in GraphQL
- 29. API with NestJS #29. Real-time updates with GraphQL subscriptions
- 30. API with NestJS #30. Scalar types in GraphQL
- 31. API with NestJS #31. Two-factor authentication
- 32. API with NestJS #32. Introduction to Prisma with PostgreSQL
- 33. API with NestJS #33. Managing PostgreSQL relationships with Prisma
- 34. API with NestJS #34. Handling CPU-intensive tasks with queues
- 35. API with NestJS #35. Using server-side sessions instead of JSON Web Tokens
- 36. API with NestJS #36. Introduction to Stripe with React
- 37. API with NestJS #37. Using Stripe to save credit cards for future use
- 38. API with NestJS #38. Setting up recurring payments via subscriptions with Stripe
- 39. API with NestJS #39. Reacting to Stripe events with webhooks
- 40. API with NestJS #40. Confirming the email address
- 41. API with NestJS #41. Verifying phone numbers and sending SMS messages with Twilio
- 42. API with NestJS #42. Authenticating users with Google
- 43. API with NestJS #43. Introduction to MongoDB
- 44. API with NestJS #44. Implementing relationships with MongoDB
- 45. API with NestJS #45. Virtual properties with MongoDB and Mongoose
- 46. API with NestJS #46. Managing transactions with MongoDB and Mongoose
- 47. API with NestJS #47. Implementing pagination with MongoDB and Mongoose
- 48. API with NestJS #48. Definining indexes with MongoDB and Mongoose
- 49. API with NestJS #49. Updating with PUT and PATCH with MongoDB and Mongoose
- 50. API with NestJS #50. Introduction to logging with the built-in logger and TypeORM
- 51. API with NestJS #51. Health checks with Terminus and Datadog
- 52. API with NestJS #52. Generating documentation with Compodoc and JSDoc
- 53. API with NestJS #53. Implementing soft deletes with PostgreSQL and TypeORM
- 54. API with NestJS #54. Storing files inside a PostgreSQL database
- 55. API with NestJS #55. Uploading files to the server
- 56. API with NestJS #56. Authorization with roles and claims
- 57. API with NestJS #57. Composing classes with the mixin pattern
- 58. API with NestJS #58. Using ETag to implement cache and save bandwidth
- 59. API with NestJS #59. Introduction to a monorepo with Lerna and Yarn workspaces
- 60. API with NestJS #60. The OpenAPI specification and Swagger
- 61. API with NestJS #61. Dealing with circular dependencies
- 62. API with NestJS #62. Introduction to MikroORM with PostgreSQL
- 63. API with NestJS #63. Relationships with PostgreSQL and MikroORM
- 64. API with NestJS #64. Transactions with PostgreSQL and MikroORM
- 65. API with NestJS #65. Implementing soft deletes using MikroORM and filters
- 66. API with NestJS #66. Improving PostgreSQL performance with indexes using MikroORM
- 67. API with NestJS #67. Migrating to TypeORM 0.3
- 68. API with NestJS #68. Interacting with the application through REPL
- 69. API with NestJS #69. Database migrations with TypeORM
- 70. API with NestJS #70. Defining dynamic modules
- 71. API with NestJS #71. Introduction to feature flags
- 72. API with NestJS #72. Working with PostgreSQL using raw SQL queries
- 73. API with NestJS #73. One-to-one relationships with raw SQL queries
- 74. API with NestJS #74. Designing many-to-one relationships using raw SQL queries
- 75. API with NestJS #75. Many-to-many relationships using raw SQL queries
- 76. API with NestJS #76. Working with transactions using raw SQL queries
- 77. API with NestJS #77. Offset and keyset pagination with raw SQL queries
- 78. API with NestJS #78. Generating statistics using aggregate functions in raw SQL
- 79. API with NestJS #79. Implementing searching with pattern matching and raw SQL
- 80. API with NestJS #80. Updating entities with PUT and PATCH using raw SQL queries
- 81. API with NestJS #81. Soft deletes with raw SQL queries
- 82. API with NestJS #82. Introduction to indexes with raw SQL queries
- 83. API with NestJS #83. Text search with tsvector and raw SQL
- 84. API with NestJS #84. Implementing filtering using subqueries with raw SQL
- 85. API with NestJS #85. Defining constraints with raw SQL
- 86. API with NestJS #86. Logging with the built-in logger when using raw SQL
- 87. API with NestJS #87. Writing unit tests in a project with raw SQL
- 88. API with NestJS #88. Testing a project with raw SQL using integration tests
- 89. API with NestJS #89. Replacing Express with Fastify
- 90. API with NestJS #90. Using various types of SQL joins
- 91. API with NestJS #91. Dockerizing a NestJS API with Docker Compose
- 92. API with NestJS #92. Increasing the developer experience with Docker Compose
- 93. API with NestJS #93. Deploying a NestJS app with Amazon ECS and RDS
- 94. API with NestJS #94. Deploying multiple instances on AWS with a load balancer
- 95. API with NestJS #95. CI/CD with Amazon ECS and GitHub Actions
- 96. API with NestJS #96. Running unit tests with CI/CD and GitHub Actions
- 97. API with NestJS #97. Introduction to managing logs with Amazon CloudWatch
- 98. API with NestJS #98. Health checks with Terminus and Amazon ECS
- 99. API with NestJS #99. Scaling the number of application instances with Amazon ECS
- 100. API with NestJS #100. The HTTPS protocol with Route 53 and AWS Certificate Manager
- 101. API with NestJS #101. Managing sensitive data using the AWS Secrets Manager
- 102. API with NestJS #102. Writing unit tests with Prisma
- 103. API with NestJS #103. Integration tests with Prisma
- 104. API with NestJS #104. Writing transactions with Prisma
- 105. API with NestJS #105. Implementing soft deletes with Prisma and middleware
- 106. API with NestJS #106. Improving performance through indexes with Prisma
- 107. API with NestJS #107. Offset and keyset pagination with Prisma
- 108. API with NestJS #108. Date and time with Prisma and PostgreSQL
- 109. API with NestJS #109. Arrays with PostgreSQL and Prisma
- 110. API with NestJS #110. Managing JSON data with PostgreSQL and Prisma
- 111. API with NestJS #111. Constraints with PostgreSQL and Prisma
- 112. API with NestJS #112. Serializing the response with Prisma
- 113. API with NestJS #113. Logging with Prisma
- 114. API with NestJS #114. Modifying data using PUT and PATCH methods with Prisma
- 115. API with NestJS #115. Database migrations with Prisma
- 116. API with NestJS #116. REST API versioning
- 117. API with NestJS #117. CORS – Cross-Origin Resource Sharing
- 118. API with NestJS #118. Uploading and streaming videos
- 119. API with NestJS #119. Type-safe SQL queries with Kysely and PostgreSQL
- 120. API with NestJS #120. One-to-one relationships with the Kysely query builder
- 121. API with NestJS #121. Many-to-one relationships with PostgreSQL and Kysely
- 122. API with NestJS #122. Many-to-many relationships with Kysely and PostgreSQL
- 123. API with NestJS #123. SQL transactions with Kysely
- 124. API with NestJS #124. Handling SQL constraints with Kysely
- 125. API with NestJS #125. Offset and keyset pagination with Kysely
- 126. API with NestJS #126. Improving the database performance with indexes and Kysely
- 127. API with NestJS #127. Arrays with PostgreSQL and Kysely
- 128. API with NestJS #128. Managing JSON data with PostgreSQL and Kysely
- 129. API with NestJS #129. Implementing soft deletes with SQL and Kysely
- 130. API with NestJS #130. Avoiding storing sensitive information in API logs
- 131. API with NestJS #131. Unit tests with PostgreSQL and Kysely
- 132. API with NestJS #132. Handling date and time in PostgreSQL with Kysely
- 133. API with NestJS #133. Introducing database normalization with PostgreSQL and Prisma
- 134. API with NestJS #134. Aggregating statistics with PostgreSQL and Prisma
- 135. API with NestJS #135. Referential actions and foreign keys in PostgreSQL with Prisma
- 136. API with NestJS #136. Raw SQL queries with Prisma and PostgreSQL range types
- 137. API with NestJS #137. Recursive relationships with Prisma and PostgreSQL
- 138. API with NestJS #138. Filtering records with Prisma
- 139. API with NestJS #139. Using UUID as primary keys with Prisma and PostgreSQL
- 140. API with NestJS #140. Using multiple PostgreSQL schemas with Prisma
- 141. API with NestJS #141. Getting distinct records with Prisma and PostgreSQL
- 142. API with NestJS #142. A video chat with WebRTC and React
- 143. API with NestJS #143. Optimizing queries with views using PostgreSQL and Kysely
- 144. API with NestJS #144. Creating CLI applications with the Nest Commander
- 145. API with NestJS #145. Securing applications with Helmet
- 146. API with NestJS #146. Polymorphic associations with PostgreSQL and Prisma
- 147. API with NestJS #147. The data types to store money with PostgreSQL and Prisma
- 148. API with NestJS #148. Understanding the injection scopes
- 149. API with NestJS #149. Introduction to the Drizzle ORM with PostgreSQL
- 150. API with NestJS #150. One-to-one relationships with the Drizzle ORM
- 151. API with NestJS #151. Implementing many-to-one relationships with Drizzle ORM
- 152. API with NestJS #152. SQL constraints with the Drizzle ORM
- 153. API with NestJS #153. SQL transactions with the Drizzle ORM
- 154. API with NestJS #154. Many-to-many relationships with Drizzle ORM and PostgreSQL
- 155. API with NestJS #155. Offset and keyset pagination with the Drizzle ORM
- 156. API with NestJS #156. Arrays with PostgreSQL and the Drizzle ORM
- 157. API with NestJS #157. Handling JSON data with PostgreSQL and the Drizzle ORM
- 158. API with NestJS #158. Soft deletes with the Drizzle ORM
- 159. API with NestJS #159. Date and time with PostgreSQL and the Drizzle ORM
- 160. API with NestJS #160. Using views with the Drizzle ORM and PostgreSQL
- 161. API with NestJS #161. Generated columns with the Drizzle ORM and PostgreSQL
- 162. API with NestJS #162. Identity columns with the Drizzle ORM and PostgreSQL
- 163. API with NestJS #163. Full-text search with the Drizzle ORM and PostgreSQL
- 164. API with NestJS #164. Improving the performance with indexes using Drizzle ORM
- 165. API with NestJS #165. Time intervals with the Drizzle ORM and PostgreSQL
- 166. API with NestJS #166. Logging with the Drizzle ORM
- 167. API with NestJS #167. Unit tests with the Drizzle ORM
- 168. API with NestJS #168. Integration tests with the Drizzle ORM
Inheritance is one of the four pillars of object-oriented programming. JavaScript has the prototype-based inheritance, and with it, one object can acquire properties of another object. Even though JavaScript has the class keyword, it still uses prototypes under the hood.
If you want to know to know more about prototypes, check out this article I wrote a few years ago.
In this article, we explain the mixin pattern in the context of TypeScript and provide examples of how we can use it with NestJS.
Creating mixins with TypeScript
Besides inheritance, JavaScript and TypeScript support another way of attaching methods and properties to classes. Following the TypeScript 2.2 RC announcement, the mixin as a function that:
- takes a constructor
- declares a class that extends that constructor
- adds members to that new class
- and returns the class itself.
The mixin pattern is also popular in languages such as Scala.
Let’s create a fundamental example of a mixin:
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type Constructor = new ( ...args: any[] ) => {}; function Person<BaseType extends Constructor>(Base: BaseType) { return class extends Base { name: string; }; } |
The above Constructor type is provided in the official documentation and makes sure that what we pass to the Person function is a class.
In a nutshell, whatever class we pass to the Person function, it becomes a person.
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const Teacher = Person( class { subject: string; } ) const John = new Teacher(); john.name = 'John'; john.subject = 'Math'; |
Constrained mixins
Above, we’ve created a Constructor type that doesn’t contain any information about the class we pass to the mixin. Sometimes, we would like the mixin to use some of the properties from the class it extends.
We can deal with the above problem by creating types that are more constrained.
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type Constructor<Type = {}> = new ( ...args: any[] ) => Type; type HasTheSubject = Constructor<{ subject: string }>; |
Thanks to creating the above types, we can define a mixin that uses the name property.
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function CanIntroduceSelf<BaseType extends HasTheSubject>(Base: BaseType) { return class extends Base { introduce() { console.log(`Hello, I teach ${this.subject}`); } }; } const Teacher = CanIntroduceSelf( class { subject: string; constructor(subject: string) { this.subject = subject; } } ) const mathTeacher = new Teacher('math'); mathTeacher.introduce(); // Hello, I teach math |
Multiple inheritance
Some programming languages implement multiple inheritance where a class can inherit from more than one parent class. Unfortunately, neither JavaScript nor TypeScript doesn’t include it.
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class Day { day: number; month: number; year: number; setDay(day: number, month: number, year: number) { this.day = day; this.month = month; this.year = year; } } class Time { hour: number; minute: number; second: number; setTime(hour: number, minute: number, second: number) { this.hour = hour; this.minute = minute; this.second = second; } } class EventTakingPlace extends Day, Time { name: string; place: string; } |
error TS1174: Classes can only extend a single class.
We can use the mixin pattern to combine multiple classes. To do that, we first need to define the applyMixin function suggested in the official documentation:
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function applyMixins(derivedConstructor: any, constructors: any) { constructors.forEach((baseConstructor) => { Object.getOwnPropertyNames(baseConstructor.prototype).forEach((name) => { Object.defineProperty( result, name, Object.getOwnPropertyDescriptor(baseConstructor.prototype, name) || Object.create(null) ); }); }); return derivedConstructor } |
I’ve made slight adjustments to the example from the documentation by writing more descriptive variable names and returning the derivedConstructor.
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onst EventTakingPlace = applyMixins( class { name: string; place: string; constructor(name: string, place: string) { this.name = name; this.place = place; } }, [Day, Time] ) const johnMayerConcert = new EventTakingPlace('John Mayer concert', 'New York'); johnMayerConcert.setDay(1, 3, 2022); johnMayerConcert.setTime(19, 30, 0); |
There is a significant drawback to using this approach, even though it is provided in the official documentation. Using the any type in the applyMixins function is a big disadvantage, and we should avoid using it as much as possible.
Instead, we can compose multiple mixins and achieve a similar result.
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function Day<BaseType extends Constructor>(Base: BaseType) { return class extends Base { day: number; month: number; year: number; setDay(day: number, month: number, year: number) { this.day = day; this.month = month; this.year = year; } } } function Time<BaseType extends Constructor>(Base: BaseType) { return class extends Base { hour: number; minute: number; second: number; setTime(hour: number, minute: number, second: number) { this.hour = hour; this.minute = minute; this.second = second; } } } const EventTakingPlace = Day( Time( class { name: string; place: string; constructor(name: string, place: string) { this.name = name; this.place = place; } } ) ) |
Mixins with NestJS
There is a good chance that you don’t find mixins very appealing. When using NestJS, they can be pretty helpful, though.
Extending the existing mixins
A big part of it is that NestJS uses mixins under the hood. A good example is the FileInterceptor. If we ever want to extend its functionalities for any reason, we need to create our mixin.
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import { FileInterceptor } from '@nestjs/platform-express'; import { Injectable, mixin, NestInterceptor, Type } from '@nestjs/common'; import { ConfigService } from '@nestjs/config'; import { MulterOptions } from '@nestjs/platform-express/multer/interfaces/multer-options.interface'; import { diskStorage } from 'multer'; interface LocalFilesInterceptorOptions { fieldName: string; path?: string; fileFilter?: MulterOptions['fileFilter']; limits?: MulterOptions['limits']; } function LocalFilesInterceptor (options: LocalFilesInterceptorOptions): Type<NestInterceptor> { @Injectable() class Interceptor implements NestInterceptor { fileInterceptor: NestInterceptor; constructor(configService: ConfigService) { const filesDestination = configService.get('UPLOADED_FILES_DESTINATION'); const destination = `${filesDestination}${options.path}` const multerOptions: MulterOptions = { storage: diskStorage({ destination }), fileFilter: options.fileFilter, limits: options.limits } this.fileInterceptor = new (FileInterceptor(options.fieldName, multerOptions)); } intercept(...args: Parameters<NestInterceptor['intercept']>) { return this.fileInterceptor.intercept(...args); } } return mixin(Interceptor); } export default LocalFilesInterceptor; |
The above code comes from API with NestJS #55. Uploading files to the server
There are a few essential things to notice above. First, we create our Interceptor class and return it using the mixin function from the @nestjs/common package. The mixin function applies the Injectable decorator under the hood.
Unfortunately, NestJS currently experiences an issue where not using @Injectable directly causes the reflect-metadata library not to pick it up. Because of that, not using @Injectable() at the top would cause the dependency injection to fail, and our configService would stay undefined. Hopefully, this bug will be resolved at some point.
Thanks to creating the above mixin, we can now easily use it in one of our controllers:
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@Post('avatar') @UseGuards(JwtAuthenticationGuard) @UseInterceptors(LocalFilesInterceptor({ fieldName: 'file', path: '/avatars', fileFilter: (request, file, callback) => { if (!file.mimetype.includes('image')) { return callback(new BadRequestException('Provide a valid image'), false); } callback(null, true); }, limits: { fileSize: Math.pow(1024, 2) // 1MB } })) async addAvatar(@Req() request: RequestWithUser, @UploadedFile() file: Express.Multer.File) { return this.usersService.addAvatar(request.user.id, { path: file.path, filename: file.originalname, mimetype: file.mimetype }); } |
Passing additional arguments
Sometimes, we would like to pass additional arguments to structures that don’t usually allow us to do that.
The official NestJS docs for authorization suggest creating separate @Roles() for setting a role and RolesGuard for checking them. Fortunately, we can solve that by creating a mixin that creates a custom guard with an additional argument.
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import Role from './role.enum'; import { CanActivate, ExecutionContext, mixin, Type } from '@nestjs/common'; import RequestWithUser from '../authentication/requestWithUser.interface'; import JwtAuthenticationGuard from '../authentication/jwt-authentication.guard'; const RoleGuard = (role: Role): Type<CanActivate> => { class RoleGuardMixin extends JwtAuthenticationGuard { async canActivate(context: ExecutionContext) { await super.canActivate(context); const request = context.switchToHttp().getRequest<RequestWithUser>(); const user = request.user; return user?.roles.includes(role); } } return mixin(RoleGuardMixin); } export default RoleGuard; |
You can find the above code in API with NestJS #56. Authorization with roles and claims
Using the above approach, we can pass arguments when using our RoleGuard. It wouldn’t be possible without using a mixin.
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@Delete(':id') @UseGuards(PermissionGuard(PostsPermission.DeletePost)) async deletePost(@Param('id', ParseIntPipe) id: number) { return this.postsService.deletePost(id); } |
Summary
Most of the time, using mixins to extend our classes might not be a fitting option. Even though that’s the case, mixins have some uses when working with the NestJS framework. Since it uses them under the hood, we might need to create our mixins to extend them. Also, mixins can come in handy when we want to pass additional arguments to structures such as guards.
In the code above, instead of PermissionGuard, it should be RoleGuard.
In the code above, c is missing on the first line.