🌼 BE TIL Day 19 0407

⬇️ Main Note
https://docs.google.com/document/d/1IQfJPSjE7EDob5GXWJAtMe1uWW8ZpABc3r7-ieIaLDo/edit

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🌿 Catch()

  async checkSoldout({ productId }) {
    // try {
    //   const product = await this.productRepository.findOne({
    //     where: { id: productId },
    //   });
    //   console.log('logic check');
    // } catch (error) {
    //   throw error.message;
    // } finally {
    //   // 특정 로직
    //   // => 에러가 떨어지던 말던 무조건 실행시켜줘야할 로직
    // }

    const product = await this.productRepository.findOne({
      where: { id: productId },
    });

    // if (product.isSoldout) {
    //   throw new HttpException(
    //     '이미 판매가 완료된 상품입니다',
    //     HttpStatus.UNPROCESSABLE_ENTITY, // 422 error
    //   );
    // }
    // ===
    if (product.isSoldout)
      throw new UnprocessableEntityException('이미 판매 완료된 상품입니다');
  }

⬇️ However we can just make a filter file so that we don't have to write try/catch every single time.

import { Catch, ExceptionFilter, HttpException } from '@nestjs/common';

@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException) {
    // 에러가 나면 nest.js에서 error를 던져주는거임
    const status = exception.getStatus();
    const message = exception.message;

    console.log('=================================');
    console.log('Error has been detected');
    console.log('Error Code: ', status);
    console.log('Error Message: ', message);
    console.log('=================================');
  }
}

☁️ Implements

1. To set this filter, go to main.ts file and enter app.useGlobalFilters();
2. Then, go to commons file and create filter folder.
3. Create http-exception.filter.ts file and create extends and implements.

• Extends : inheritance (상속)
• Implements : (구현)
  : This one's different from inheritance. Since it isn't being extended, there can be diverse implements.
• Don't have to be in the format of typescript.

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { HttpExceptionFilter } from './commons/filter/http-exception.filter';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.useGlobalFilters(new HttpExceptionFilter()); // 에러가 났을때 리턴할 값
  // class 라서 new 로 declare
  await app.listen(3000);
}
bootstrap();

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🌿 soft delete

const result = await this.productRepository.softDelete({ id: productId });
return result.affected ? true : false;

softDelete itself is a function that is included in node modules.
soft delete is different from actually deleting the data.

• soft delete is not completely removing the data from the database. To frontend, it seems like the data is gone, but the data is actually hidden inside the database.
• Inside the database, there is isDeleted column, which saves the data of deletion. If the data is soft-deleted, there occurs a date, which is the deletion date.
• If frontend tries to use fetchProductsWithDeleted API, it's able to see product lists with the deleted ones.
• So basically it's just pretending to be deleted.

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🌿 Join

// Many to one Joining
async findOne({ productId }) {
   return await this.productRepository.findOne({
     where: { id: productId },
     relations: ['productSaleslocation', 'productCategory'],
   });
 }

• relations should be delcared to tell the computer to join those tables into one.

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