DFValidator

A powerful, fluent validation library for Delphi applications that makes data validation clean and easy.

Features

• Fluent API for building validation rules
• Built-in validators for common data types (strings, integers, dates, emails)
• Easy extensibility to create custom validators
• Detailed validation results with custom error messages
• Zero external dependencies

Installation

1. Add DFValidator.pas to your project
2. Add DFValidator to your unit's uses clause
3. Start validating!

Quick Example

uses
  DFValidator;

// Example 1: Validate username
var
  Username: string;
  ValidationResult: TDFValidationResult;
begin
  Username := 'john123';
  ValidationResult := TDFValidate.String
    .Required
    .MinLength(5)
    .MaxLength(20)
    .Matches('^[a-zA-Z0-9_]+$')
    .Validate(Username);
    
  if not ValidationResult.IsValid then
    ShowMessage(ValidationResult.ErrorMessage);
end;

// Example 2: Validate age
var
  Age: Integer;
  ValidationResult: TDFValidationResult;
begin
  Age := 15;
  ValidationResult := TDFValidate.Integer
    .Min(18)
    .Max(120)
    .Validate(Age);
    
  if not ValidationResult.IsValid then
    ShowMessage(ValidationResult.ErrorMessage);  // Will show error since age is under 18
end;

// Example 3: Validate email
var
  Email: string;
  ValidationResult: TDFValidationResult;
begin
  Email := 'user@example.com';
  ValidationResult := TDFValidate.Email
    .Required
    .Validate(Email);
    
  if not ValidationResult.IsValid then
    ShowMessage(ValidationResult.ErrorMessage);
end;

Available Validators

String Validator

• Required() - Makes the string required (non-empty)
• MinLength(n) - Sets minimum string length
• MaxLength(n) - Sets maximum string length
• Matches(pattern) - Validates string against a regular expression pattern

Integer Validator

• Min(n) - Sets minimum value
• Max(n) - Sets maximum value

Date Validator

• After(date) - Date must be after specified date
• Before(date) - Date must be before specified date

Email Validator

• Pre-configured string validator with email pattern

Creating Custom Validators

You can easily extend the library with your own validators:

type
  TPhoneValidator = class(TDFValidator<string>)
  private
    FCountryCode: string;
  public
    constructor Create;
    function Validate(const Value: string): TDFValidationResult; override;
    function ForCountry(const ACountryCode: string): TPhoneValidator;
  end;

License

MIT License

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.