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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/LizandroCanul/back_sdo/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

The API uses class-validator and class-transformer to automatically validate incoming requests through DTOs (Data Transfer Objects). Validation is configured globally in main.ts.

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Global Validation Configuration

Validation is enabled application-wide with these settings: 
import { ValidationPipe } from '@nestjs/common';

app.useGlobalPipes(
  new ValidationPipe({
    whitelist: true,              // Removes unknown properties
    forbidNonWhitelisted: true,   // Throws error for unknown properties
    transform: true,              // Auto-converts types (crucial for nested DTOs)
  }),
);
The transform: true option is critical for nested DTOs and type conversions. It automatically converts plain JSON objects to DTO class instances.

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Configuration Options Explained

Automatically strips properties that don’t have validation decorators.Example:
// Request body
{
  "nombre": "Test",
  "hackerField": "malicious" // This will be removed
}
Instead of silently removing unknown properties, it throws a 400 Bad Request error.Response:
{
  "statusCode": 400,
  "message": ["property hackerField should not exist"],
  "error": "Bad Request"
}
Converts incoming data to the expected types and DTO instances.Transformations:
  • "123" → 123 (string to number)
  • "true" → true (string to boolean)
  • Plain objects → DTO class instances

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Common Validation Decorators

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String Validation

@IsString()
@IsNotEmpty()
@MaxLength(255)
nombre: string;

​
Number Validation

@IsNumber()
@IsNotEmpty()
municipioId: number;

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Optional Fields

@IsString()
@IsOptional()
descripcion?: string;

​
Enum Validation

export enum TipoGeometria {
  PUNTO = 'PUNTO',
  RUTA = 'RUTA',
  POLIGONO = 'POLIGONO',
}

@IsEnum(TipoGeometria)
@IsOptional()
tipoGeometria?: TipoGeometria;

​
Boolean Validation

@IsBoolean()
@IsOptional()
activo?: boolean;

​
Nested DTO Validation

For complex objects with nested DTOs, use @ValidateNested() with @Type(): 
import { Type } from 'class-transformer';
import { IsArray, ValidateNested, IsOptional } from 'class-validator';
import { CreateObraUbicacionDto } from './create-obra-ubicacion.dto';

export class CreateObraDto {
  @IsString()
  @IsNotEmpty()
  nombre: string;

  // Nested array of location DTOs
  @IsArray()
  @ValidateNested({ each: true }) // Validates each item in array
  @Type(() => CreateObraUbicacionDto) // Transforms to DTO instances
  @IsOptional()
  ubicaciones?: CreateObraUbicacionDto[];
}
Without @Type() decorator, nested DTOs won’t be validated. The transform: true option in ValidationPipe requires this decorator to work with nested objects.

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Real-World DTO Examples

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CreateUserDto

import { IsEmail, IsString, MinLength, IsOptional, IsIn, IsBoolean } from 'class-validator';

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

  @IsString()
  @IsEmail()
  email: string;

  @IsString()
  @MinLength(6, { message: 'La contraseña debe tener al menos 6 caracteres' })
  password: string;

  @IsOptional()
  @IsString()
  @IsIn(['admin', 'user'])
  roles?: string;

  @IsOptional()
  @IsBoolean()
  isActive?: boolean;
}
Location: /home/daytona/workspace/source/src/users/dto/create-user.dto.ts:1

​
CreateMunicipioDto

import { IsString, IsNotEmpty, IsNumber, Min, Max, IsOptional, IsBoolean } from 'class-validator';
import { Transform } from 'class-transformer';

export class CreateMunicipioDto {
  @IsString()
  @IsNotEmpty()
  @Transform(({ value }) => value?.trim())
  nombre: string;

  @IsNumber()
  @IsNotEmpty()
  @Min(-90)
  @Max(90)
  latitud: number;

  @IsNumber()
  @IsNotEmpty()
  @Min(-180)
  @Max(180)
  longitud: number;

  @IsBoolean()
  @IsOptional()
  activo?: boolean;
}
Location: /home/daytona/workspace/source/src/municipios/dto/create-municipio.dto.ts:1

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CreateObraDto (Complex)

import { IsString, IsNotEmpty, IsArray, ValidateNested, IsNumber, IsOptional, IsPositive, Min, MaxLength } from 'class-validator';
import { Type } from 'class-transformer';
import { CreateObraUbicacionDto } from './create-obra-ubicacion.dto';

export class CreateObraDto {
  // Fiscal year
  @IsNumber()
  @IsNotEmpty()
  ejercicioFiscalId: number;

  // Unique key
  @IsString()
  @IsNotEmpty()
  @MaxLength(50)
  claveUnica: string;

  // Name
  @IsString()
  @IsNotEmpty()
  @MaxLength(255)
  nombre: string;

  // Description
  @IsString()
  @IsOptional()
  descripcion?: string;

  // Department
  @IsNumber()
  @IsNotEmpty()
  dependenciaId: number;

  // Budget
  @IsNumber({ maxDecimalPlaces: 2 })
  @IsPositive()
  @Min(0)
  monto: number;

  // Municipality
  @IsNumber()
  @IsNotEmpty()
  municipioId: number;

  // Project type (optional)
  @IsNumber()
  @IsOptional()
  tipoProyectoId?: number;

  // Status
  @IsNumber()
  @IsNotEmpty()
  estatusObraId: number;

  // Nested locations array
  @IsArray()
  @ValidateNested({ each: true })
  @Type(() => CreateObraUbicacionDto)
  @IsOptional()
  ubicaciones?: CreateObraUbicacionDto[];
}
Location: /home/daytona/workspace/source/src/obras/dto/create-obra.dto.ts:1

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Validation Error Responses

When validation fails, NestJS returns a standardized error response: 
{
  "statusCode": 400,
  "message": [
    "email must be an email"
  ],
  "error": "Bad Request"
}

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Custom Validation Messages

You can customize error messages using the decorator options: 
@MinLength(6, { message: 'La contraseña debe tener al menos 6 caracteres' })
password: string;

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Best Practices

Always Use DTOs

Never accept raw request bodies. Create a DTO for every endpoint that accepts data.

Be Explicit

Use @IsNotEmpty() for required fields and @IsOptional() for optional ones.

Type Safety

Combine validation with TypeScript types for compile-time and runtime safety.

Nested Validation

Don’t forget @Type() and @ValidateNested() for nested objects and arrays.
The transform: true configuration (set in main.ts:13) is essential for:
  • Auto-converting query parameters from strings
  • Transforming nested DTOs
  • Type coercion (string to number, etc.)

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Common Validation Patterns

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Password Validation

@IsString()
@MinLength(6, { message: 'La contraseña debe tener al menos 6 caracteres' })
password: string;

​
Geographic Coordinates

@IsNumber()
@Min(-90)
@Max(90)
latitud: number;

@IsNumber()
@Min(-180)
@Max(180)
longitud: number;

​
Money/Currency

@IsNumber({ maxDecimalPlaces: 2 })
@IsPositive()
@Min(0)
monto: number;

​
Trimmed Strings

@IsString()
@IsNotEmpty()
@Transform(({ value }) => value?.trim())
nombre: string;

​
Next Steps

Database Schema

Learn about entity relationships

Error Handling

Understand error responses

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