Vatsalya-singhi

import { Controller, Post, Body, UsePipes, ValidationPipe } from '@nestjs/common';
import { CreateUserDto } from './create-user.dto';

@Controller('users')
export class UsersController {
  @Post()
  @UsePipes(new ValidationPipe()) // Apply validation
  create(@Body() createUserDto: CreateUserDto) {
    return { message: 'User created', data: createUserDto };
  }

Vatsalya-singhi

import { IsString, IsInt, MinLength, Min } from 'class-validator';

export class CreateUserDto {
  @IsString()
  @MinLength(3)
  name: string;

  @IsInt()
  @Min(18)
  age: number;

Vatsalya-singhi

// Custom Pipe used in a Controller
import { Controller, Post, Body } from '@nestjs/common';
import { UppercasePipe } from './uppercase.pipe';

@Controller('users')
export class UsersController {
  @Post()
  create(@Body('name', new UppercasePipe()) name: string) {
    return { message: 'User created', name };
  }

Vatsalya-singhi

// convert strings to uppercase
import { PipeTransform, Injectable, ArgumentMetadata } from '@nestjs/common';

@Injectable()
export class UppercasePipe implements PipeTransform {
  transform(value: any, metadata: ArgumentMetadata) {
    return typeof value === 'string' ? value.toUpperCase() : value;
  }
}

Vatsalya-singhi

import { Controller, Get, Param, ParseIntPipe } from '@nestjs/common';

@Controller('users')
export class UsersController {
  @Get(':id')
  findOne(@Param('id', ParseIntPipe) id: number) {
    return { message: `Fetching user with ID ${id}` };
  }
}

Vatsalya-singhi

@Get()
@UseFilters(HttpExceptionFilter) // Apply to only this method
findAll() {
  throw new HttpException('Users not found', HttpStatus.NOT_FOUND);
}

Vatsalya-singhi

import { Controller, Get, UseFilters, HttpException, HttpStatus } from '@nestjs/common';
import { HttpExceptionFilter } from './http-exception.filter';

@Controller('users')
@UseFilters(HttpExceptionFilter) // Apply to all methods in this controller
export class UsersController {
  @Get()
  findAll() {
    throw new HttpException('Users not found', HttpStatus.NOT_FOUND);
  }

Vatsalya-singhi

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

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.useGlobalFilters(new HttpExceptionFilter()); // Apply globally
  await app.listen(3000);
}

Vatsalya-singhi

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

@Catch(HttpException) // Catches only HTTP-related exceptions
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();
    const status = exception.getStatus();
    const message = exception.getResponse();

Vatsalya-singhi

import { MiddlewareConsumer, Module, NestModule } from '@nestjs/common';
import { UsersController } from './users.controller';
import { UsersService } from './users.service';
import { LoggerMiddleware } from './logger.middleware';

@Module({
  controllers: [UsersController],
  providers: [UsersService],
})
export class UsersModule implements NestModule {