# Learning NestJS, Part3
###### tags: `Nestjs`
## 學習資源
[NestJS: The Complete Developer's Guide](https://www.udemy.com/course/nestjs-the-complete-developers-guide/) on Udemy

## 使用TypeORM操作資料
### 流程
1. 建立(entity_name).entity.ts的檔案
2. 從'typeorm'引入所需的decorator，ex: PrimaryGeneratedColumn、Entity、Column

// user.entity.ts
import {
  AfterInsert,
  Entity,
  Column,
  PrimaryGeneratedColumn,
  AfterRemove,
  AfterUpdate,
} from 'typeorm';

@Entity()
export class User {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  email: string;

  @Column()
  password: string;
  
  @AfterInsert()
  logInsert() {
    console.log('Inserted User with id', this.id);
  }

  @AfterUpdate()
  logUpdate() {
    console.log('Updated User with id', this.id);
  }

  @AfterRemove()
  logRemove() {
    console.log('Removed User with id', this.id);
  }
}

**AfterInsert、AfterRemove、AfterUpdate**此三個為Hooks
當User資料有變動時(insert、remove、update)，則會在console.log出對應之訊息

**Hooks的觸發狀況**


3. 在user.module.ts中引入相關套件及entity

// user.module.ts
...
import { TypeOrmModule } from '@nestjs/typeorm';
import { UsersService } from './users.service';
import { User } from './user.entity';
...
@Module({
  // This will create repository for us
  imports: [TypeOrmModule.forFeature([User])],
...

4. 在app.module.ts中引入相關套件及entity

import { TypeOrmModule } from '@nestjs/typeorm';
...
import { User } from './users/user.entity';
import { Report } from './reports/report.entity';
...
@Module({
  imports: [
    TypeOrmModule.forRoot({
      type: 'sqlite',
      database: 'db.sqlite',
      entities: [User, Report],
      synchronize: true,
    }),
    ...
...

[TypeORM Decorators Reference](https://orkhan.gitbook.io/typeorm/docs/decorator-reference)

### 請求送出的流程圖

## 實例序列化

教案中使用的plainToClass函式現已改為使用plainToInstance