Basic CRUD API - Nest.js
$ npm install# development
$ npm run start
# watch mode
$ npm run start:dev
# production mode
$ npm run start:prod# unit tests
$ npm run test
# e2e tests
$ npm run test:e2e
# test coverage
$ npm run test:covNest is an MIT-licensed open source project. It can grow thanks to the sponsors and support by the amazing backers. If you'd like to join them, please read more here.
- Author - Kamil Myśliwiec
- Website - https://nestjs.com
- Twitter - @nestframework
Nest is MIT licensed.
Automatic Validation
- Use global validation
- Class that describes the different properties that the request body should have (DTO)
- Use validation rules in the class
- Apply class to the request handler
Packages
-
class-transformer -> is a simple package that takes a plain object and converts it into an instance of a class. link: https://www.npmjs.com/package/class-transformer
-
class-validator -> allows use of decorator and non-decorator based validation. Internally uses validator.js to perform validation. Class-validator works on both browser and node.js platforms. link: https://www.npmjs.com/package/class-validator
How validation works?
- Use class-transformer to turn the body into an instance of the DTO class
- Use class-validator to validate the instance
- If there are validation errors repsond immediately otherwise provide body to request handler.
tsconfig.json
- "experimentalDecorators" -> this line of code in this configuration file allows a very small amount of type information to "make it" from the typescript world to the javascript world.
Services
- It is a class
- #1 place to put any business logic
- Uses one or more repositories to find or store data
Repositories
- It is a class
- #1 place to put storage-related logic
- Usually ends up being a TypeORM entity, a Mongoose schema or similar
SOLID
- I -> Inversion of Control Principle: Classes should not create instances of its dependencies on its own
Nest Dependency Injection Container/Injector
- Contains list of classes and their dependencies (list: class1 -> dependencies1, class2 -> dependencies2, and so on...)
- Contains list of created instances
DI Container Flow
- At startup, register all classes with the container
- Container will figure out what each dependency each class has
- Ask the container to create an instance of a class
- Container creates all required dependencies and returns the instance
- Container will hold onto the created dependency instances and reuse them if needed (The payout of all of these DI stuff is shown while writing tests =P)