- 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
With GraphQL, we model our API as a graph. Within a schema, we have various types of nodes that can relate to each other. While the fields in our query might have sub-fields, at some point, we want to work on concrete data. We refer to the type that describes an individual value as the scalar. It does not have any sub-fields and represents a leaf in the graph. In some way, scalars are similar to primitive values.
A leaf in a graph is a node that does not have any children
GraphQL supports a set of scalar types out of the box:
-
Int: a signed 32-bit integer
- can’t hold fractional values,
-
Float: signed double-precision floating-point value,
- can hold fractional values,
- Boolean: either true or false,
- ID: represents a unique identifier, serialized in the same way as String.
Scalar types in NestJS
We’ve already used some of the above in the previous parts of this series.
post.model.ts
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import { Field, Int, ObjectType } from '@nestjs/graphql'; import { User } from '../../users/models/user.model'; @ObjectType() export class Post { @Field(() => Int) id: number; @Field() title: string; @Field(() => [String]) paragraphs: string[]; @Field(() => Int) authorId: number; @Field() author: User; } |
An important thing to look into above is how we use the @Field() decorator. We don’t have to specify the exact scalar type for strings and booleans. Since we can represent numbers either as an Int or Float, we should pass an additional parameter to the @Field() decorator.
If we don’t pass the parameter with the type, NestJS by default would use the Float scalar. We could change this behaviour by setting the numberScalarMode parameter to integer.
Handling dates with NestJS and TypeORM
Under the hood, NestJS implements additional scalars that we should be aware of:
-
GraphQLISODateTime: a date-time UTC string,
- NestJS uses it by default to represent the Date type,
-
GraphQLTimestamp: a numeric string representing the time and date as the number of milliseconds from the start of the UNIX epoch,
- we can use it instead of GraphQLISODateTime.
To observe the behavior of GraphQLISODateTime and GraphQLTimestamp, let’s add a field to our PostEntity.
So far in this series, we’ve been using TypeORM. In the documentation, we can see that it has a @CreateDateColumn() decorator. It allows us to access the entity’s insertion time. TypeORM sets its value under the hood.
post.entity.ts
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import { Entity, PrimaryGeneratedColumn, CreateDateColumn } from 'typeorm'; @Entity() class Post { @PrimaryGeneratedColumn() public id: number; @CreateDateColumn({ type: 'timestamp' }) createdAt: Date; // ... } export default Post; |
The last thing to do is to modify our model:
post.model.ts
1 2 3 4 5 6 7 8 9 10 11 12 |
import { Field, Int, ObjectType } from '@nestjs/graphql'; @ObjectType() export class Post { @Field(() => Int) id: number; @Field() createdAt: Date; // ... } |
Thanks to doing all of the above, we can now query the creation date of our posts.
By default, NestJS used the custom GraphQLISODateTime scalar. We could change this behavior and use timestamps instead by setting the dateScalarMode option.
app.module.ts
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import { Module } from '@nestjs/common'; import { ConfigModule, ConfigService } from '@nestjs/config'; import { GraphQLModule } from '@nestjs/graphql'; import { join } from 'path'; @Module({ imports: [ GraphQLModule.forRootAsync({ imports: [ConfigModule], inject: [ConfigService], useFactory: ( configService: ConfigService, ) => ({ playground: Boolean(configService.get('GRAPHQL_PLAYGROUND')), autoSchemaFile: join(process.cwd(), 'src/schema.gql'), installSubscriptionHandlers: true, buildSchemaOptions: { dateScalarMode: 'timestamp', } }) }), // ... ], controllers: [], providers: [], }) export class AppModule {} |
Defining custom scalars
Aside from using the built-in types, we can also create our own scalars. As an example, let’s replicate the functionalities of the GraphQLTimestamp type.
To do that, we need to create a class that implements the CustomScalar interface. it consists of three methods:
-
serialize
- its job is to parse the result when sending it to the client
-
parseValue
- parses values received from the client during mutation provided as variables in a JSON format
-
parseLiteral
- also parsers the values provided during mutation, but in the form of hard-coded values as a part of the Abstract Syntax Tree (AST)
Let’s mimic the Timestamp scalar that NestJS has under the hood:
timestamp.scalar.ts
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import { Scalar, CustomScalar } from '@nestjs/graphql'; import { Kind, ValueNode } from 'graphql'; @Scalar('Timestamp', () => Date) export class Timestamp implements CustomScalar<number, Date> { description = '`Date` type as integer. Type represents date and time as number of milliseconds from start of UNIX epoch.'; serialize(value: Date) { return value instanceof Date ? value.getTime() : null; } parseValue(value: string | number | null) { try { const number = Number(value); return value !== null ? new Date(number) : null; } catch { return null; } } parseLiteral(valueNode: ValueNode) { if ( valueNode.kind === Kind.INT || valueNode.kind === Kind.STRING ) { try { const number = Number(valueNode.value); return new Date(number); } catch { return null; } } return null; } } |
We also need to add the Timestamp scalar to the providers array in our AppModule.
Above, we should look a bit deeper into the parseLiteral method. Its argument is of the type ValueNode and describes the input that the user added in the mutation.
To check its type, we need to compare the valueNode.kind with the Kind exported with the graphql library.
Testing our Timestamp scalar
To create a valid use case for parseValue and parseLiteral, let’s add a date field that the client can set. An example of that could be scheduledDate in the Post entity.
post.entity.ts
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import { Column, Entity, PrimaryGeneratedColumn, CreateDateColumn } from 'typeorm'; @Entity() class Post { @PrimaryGeneratedColumn() public id: number; @CreateDateColumn({ type: 'timestamp' }) createdAt: Date; @Column({ type: 'timestamp', nullable: true }) scheduledDate?: Date; } export default Post; |
We also need to add the new field to the model and the input.
post.model.ts
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 |
import { Field, Int, ObjectType } from '@nestjs/graphql'; @ObjectType() export class Post { @Field(() => Int) id: number; @Field() createdAt: Date; @Field({ nullable: true }) scheduledDate?: Date; // ... } |
post.input.ts
1 2 3 4 5 6 7 8 9 10 11 12 13 |
import { InputType, Field } from '@nestjs/graphql'; @InputType() export class CreatePostInput { @Field() title: string; @Field(() => [String]) paragraphs: string[]; @Field({ nullable: true }) scheduledDate?: Date; } |
First, let’s try out the parseLiteral method. To do that, we need to create a mutation while hardcoding the values:
Performing the above mutation causes the parseLiteral method to run with the following argument:
1 2 3 4 |
{ type: Kind.INT, value: 1613919356099 } |
To test the parseValue method, we need to pass the values as a set of variables:
Summary
In this article, we’ve looked into scalar types in GraphQL and how to apply them in NestJS. We’ve gone through both the basic scalars and the custom ones built into NestJS. On top of that, we’ve created our own custom scalar. By doing so, we’ve got to know the difference between sending the mutation input with variables and inline values.
Will you describe usage of Server-Sent Events?