Validation Pipes

Nidus provides a rich validation system built on Delphi RTTI attributes. Annotate DTO class properties with decorator attributes and register a global TValidationPipe — Nidus will validate incoming request data automatically before route handlers run.

Enabling global validation

GetNidus
  .UsePipes(TValidationPipe.Create)
  .Start(TAppModule.Create);

Source: TNidus.UsePipes stores the IValidationPipe in TRegister. On every request, LoadRouteModule calls FRegister.Pipe.Validate(LRouteHandle, FRequest).

Annotating a DTO

uses
  Nidus.Decorator.IsEmail,
  Nidus.Decorator.IsNotEmpty,
  Nidus.Decorator.IsStrongPassword,
  Nidus.Decorator.IsUUID,
  Nidus.Decorator.IsInteger;

type
  TCreateUserDto = class
  private
    FName: string;
    FEmail: string;
    FPassword: string;
    FAge: Integer;
  public
    [IsNotEmpty('Name is required!')]
    property Name: string read FName write FName;

    [IsEmail('Invalid email address!')]
    property Email: string read FEmail write FEmail;

    [IsStrongPassword('Password is too weak!')]
    property Password: string read FPassword write FPassword;

    [IsInteger('Age must be an integer')]
    property Age: Integer read FAge write FAge;
  end;

Full decorator catalogue

Nidus ships with over 60 built-in decorators under Source/Pipes/Decorators/. Key families:

String validators

Decorator	Unit
[IsNotEmpty(msg)]	Nidus.Decorator.IsNotEmpty
[IsEmpty(msg)]	Nidus.Decorator.IsEmpty
[IsAlpha(msg)]	Nidus.Decorator.IsAlpha
[IsAlphaNumeric(msg)]	Nidus.Decorator.IsAlphaNumeric
[IsAscii(msg)]	Nidus.Decorator.IsAscii
[Contains(sub, msg)]	Nidus.Decorator.Contains
[IsLength(AValueMin, AValueMax, msg)]	Nidus.Decorator.IsLength

Format validators

Decorator	Unit
[IsEmail(msg)]	Nidus.Decorator.IsEmail
[IsUUID(msg)]	Nidus.Decorator.IsUUID
[IsIP(msg)]	Nidus.Decorator.IsIP
[IsURL(msg)]	Nidus.Decorator.IsURL
[IsISO8601(msg)]	Nidus.Decorator.IsISO8601
[IsDate(msg)]	Nidus.Decorator.IsDate
[IsDateString(msg)]	Nidus.Decorator.IsDateString
[IsHexColor(msg)]	Nidus.Decorator.IsHexColor
[IsHexadecimal(msg)]	Nidus.Decorator.IsHexadecimal
[IsCreditCard(msg)]	Nidus.Decorator.IsCreditCard
[IsIban(msg)]	Nidus.Decorator.IsIban
[IsBic(msg)]	Nidus.Decorator.IsBic
[IsEAN(msg)]	Nidus.Decorator.IsEAN
[IsISBN(msg)]	Nidus.Decorator.IsIsbn

Type validators

Decorator	Unit
[IsInteger(msg)]	Nidus.Decorator.IsInteger
[IsNumber(msg)]	Nidus.Decorator.IsNumber
[IsBoolean(msg)]	Nidus.Decorator.IsBoolean
[IsBooleanString(msg)]	Nidus.Decorator.IsBooleanString
[IsEnum(TEnum, msg)]	Nidus.Decorator.IsEnum
[IsInstance(TClass, msg)]	Nidus.Decorator.IsInstance

Crypto / encoding

Decorator	Unit
[IsBase64(msg)]	Nidus.Decorator.IsBase64
[IsBase32(msg)]	Nidus.Decorator.IsBase32
[IsBase58(msg)]	Nidus.Decorator.IsBase58
[IsHash(alg, msg)]	Nidus.Decorator.IsHash
[IsBTCAddress(msg)]	Nidus.Decorator.IsBTCAddress
[IsEthereumAddress(msg)]	Nidus.Decorator.IsEethereumAddress

Array validators

Decorator	Unit
[IsArray(msg)]	Nidus.Decorator.IsArray
[IsArrayNotEmpty(msg)]	Nidus.Decorator.IsArrayNotEmpty
[IsArrayUnique(msg)]	Nidus.Decorator.IsArrayUnique
[IsArrayMinSize(n, msg)]	Nidus.Decorator.IsArrayMinSize
[IsArrayMaxSize(n, msg)]	Nidus.Decorator.IsArrayMaxSize
[ArrayContains(val, msg)]	Nidus.Decorator.ArrayContains
[ArrayNotContains(val, msg)]	Nidus.Decorator.ArrayNotContains

Validation error response

When any property fails validation, TValidationPipe.BuildMessages aggregates the error messages and LoadRouteModule returns a TReturnPair failure wrapping EBadRequestException. The Horse driver translates this to an HTTP 400 response with a JSON body.

Custom validators

Implement IValidatorConstraint (from Nidus.Validation.Interfaces) to write your own constraint, then create a custom attribute that references it.

The concrete base class TValidatorConstraint (from Nidus.Validator.Constraint) implements the interface and declares Validate as virtual; abstract:

// 1. Implement the constraint class
type
  TMyConstraint = class(TValidatorConstraint)
  public
    function Validate(const Value: TValue;
      const Args: IValidationArguments): TResultValidation; override;
  end;

function TMyConstraint.Validate(const Value: TValue;
  const Args: IValidationArguments): TResultValidation;
begin
  if {condition} then
    Result.Success(True)
  else
    Result.Failure(Args.Message);
end;

// 2. Create a matching attribute
type
  MyRuleAttribute = class(IsAttribute)
  public
    constructor Create(const AMessage: string = ''); override;
    function Validation: TValidation; override;
  end;

constructor MyRuleAttribute.Create(const AMessage: string);
begin
  inherited Create(AMessage);
  FTagName := 'MyRule';
end;

function MyRuleAttribute.Validation: TValidation;
begin
  Result := TMyConstraint;
end;

Transform pipes

Two built-in transform pipes convert raw request strings to typed values:

Class	Unit	Purpose
TParseJsonPipe	Nidus.Parse.Json.Pipe	Deserialize a JSON body string
TParseIntegerPipe	Nidus.Parse.Integer.Pipe	Parse a string route param to Integer

Source barrel: Nidus.Validation.Include.