QFieldValidator

The most awesome validation engine ever created for C++.

Motivation

Qt is one of the best frameworks for C++ mostly used for GUI and Mobile application but also usefull for developing high-end backends. I looked for a good validation library to be used in companion with QRestServer but I couldn't find any good one, So I developed this library based on Respect\Validation php library.

Features

TOC

Simple validation

The Hello World validator is something like this:

    QString foo = "bar";
    QFieldValidator().notEmpty().validate(foo);

Chained validation

It is possible to use validators in a chain. Sample below validates a string containing numbers and letters, no whitespace and length between 1 and 15.

    QString foo = "bar";
    QFieldValidator().asciiAlNum().minLenght(1).maxLenght(15).validate(foo);

Conditioanl validators

There are three conditional methods that can be used for complex rules:

oneOf(const QList<QFieldValidator>& _validators) Used when the value can match with any of the specified validation rules

      QFieldValidator().oneOf({
          QFieldValidator().email(),
          QFieldValidator().mobile()
      }).isValid("09136477280");

allOf(const QList<QFieldValidator>& _validators) This is an alias for chained rules

      QFieldValidator().allOf({
          QFieldValidator().asciiAlNum(),
          QFieldValidator().minLenght(5)
      }).isValid("09136477280");

when(const QFieldValidator& _if, const QFieldValidator& _then, const QFieldValidator& _else) For binary conditions when to validate based on the type of value

      QFieldValidator().when({
          QFieldValidator().email(),
          QFieldValidator().emailNotDomain("gmail.com",true),
          QFieldValidator().mobile()
      }).isValid("09136477280");

Validation methods

There are two main methods to validate a value:

bool isValid(const QVariant& _value, const QString& _fieldName = QString()) This method will validate without throwing an excption. returns false on any error and error message can be accessed by errorMessage() method
void validate(const QVariant& _value, const QString& _fieldName = QString()); This method will throw an excption on any error with a full description of the error as exception message

Validating object attributes

Given this simple object:

const char user[]="{\"name\": \"Mehran\"},{\"mobile\": \"09126174582\"}";

It is possible to validate its attributes in a single chain:

QFieldValidator().hasKey("name")
                 .hasKey("mobile", QFieldValidator().mobile())
                 .validate(user);

Or with more complex and nested objects: Given this simple object:

QJsonObject user={
    {"name", "Mehran"},
    {"info", QVariantMap({
                             {"mobile", "09126174582"}
                         })
    }
};

It is possible to validate its attributes in a single chain:

QFieldValidator().hasKey("name")
                 .hasNestedKey("info.mobile", QFieldValidator().mobile())
                 .validate(user);

Input optional

All chained rules are mandatory in QfieeldValidator so if you want to treat a value as optional you can use QFieldValidator::optional() rule:

QString sampleEmpty;
QString sampleString = "abcd";
QString sampleMobile = "09126578425";

QFieldValidator mobileValidator = QFieldValidator().mobile();

mobileValidator.isValid(sampleEmpty);  //false as mobile number is empty
mobileValidator.isValid(sampleString); //false as it is no mobile
mobileValidator.isValid(sampleMobile); //true

QFiledValidator().optional(mobileValidator).isValid(sampleEmpty)  //true as was optional
QFiledValidator().optional(mobileValidator).isValid(sampleString) //false as it is incorrect
QFiledValidator().optional(mobileValidator).isValid(sampleMobile) //true

Validator reuse

Once created, you can reuse your validator anywhere. Remember mobileValidator ?

mobileValidator.isValid("");  //false as mobile number is empty
mobileValidator.isValid("abcd"); //false as it is no mobile
mobileValidator.isValid("0915154650"); //true

Exception types