- Qt 5.15
- Qt GUI
- C++ Classes
- QDoubleValidator
- Qt 5.15.18 Reference Documentation

# QDoubleValidator Class

The QDoubleValidator class provides range checking of floating-point numbers. More...

Header: | #include <QDoubleValidator>
qmake: | QT += gui
Inherits: | QValidator

- List of all members, including inherited members

## Public Types

enum | Notation { StandardNotation, ScientificNotation }

## Properties

- bottom : double
- decimals : int
- notation : Notation
- top : double

## Public Functions

| QDoubleValidator(double bottom, double top, int decimals, QObject *parent = nullptr)
| QDoubleValidator(QObject *parent = nullptr)
virtual | ~QDoubleValidator()
double | bottom() const
int | decimals() const
Notation | notation() const
void | setBottom(double)
void | setDecimals(int)
void | setNotation(Notation)
virtual void | setRange(double minimum, double maximum, int decimals = 0)
void | setTop(double)
double | top() const

## Reimplemented Public Functions

virtual QValidator::State | validate(QString &input, int &pos) const override

## Signals

void | bottomChanged(double bottom)
void | decimalsChanged(int decimals)
void | notationChanged(QDoubleValidator::Notation notation)
void | topChanged(double top)

## Detailed Description

QDoubleValidator provides an upper bound, a lower bound, and a limit on the number of digits after the decimal point. It does not provide a fixup() function.

You can set the acceptable range in one call with setRange(), or with setBottom() and setTop(). Set the number of decimal places with setDecimals(). The validate() function returns the validation state.

QDoubleValidator uses its locale() to interpret the number. For example, in the German locale, "1,234" will be accepted as the fractional number 1.234. In Arabic locales, QDoubleValidator will accept Arabic digits.

Note: The QLocale::NumberOptions set on the locale() also affect the way the number is interpreted. For example, since QLocale::RejectGroupSeparator is not set by default, the validator will accept group separators. It is thus recommended to use QLocale::toDouble() to obtain the numeric value.

See also QIntValidator, QRegExpValidator, QLocale::toDouble(), and Line Edits Example.

## Member Type Documentation

### enum QDoubleValidator::Notation

This enum defines the allowed notations for entering a double.

Constant | Value | Description
--- | --- | ---
`QDoubleValidator::StandardNotation` | `0` | The string is written as a standard number (i.e. 0.015).
`QDoubleValidator::ScientificNotation` | `1` | The string is written in scientific form. It may have an exponent part(i.e. 1.5E-2).

This enum was introduced or modified in Qt 4.3.

## Property Documentation

### bottom : double

This property holds the validator's minimum acceptable value

By default, this property contains a value of -infinity.

Access functions:

double | bottom() const
void | setBottom(double)

Notifier signal:

void | bottomChanged(double bottom)

See also setRange().

### decimals : int

This property holds the validator's maximum number of digits after the decimal point

By default, this property contains a value of 1000.

Access functions:

int | decimals() const
void | setDecimals(int)

Notifier signal:

void | decimalsChanged(int decimals)

See also setRange().

### notation : Notation

This property holds the notation of how a string can describe a number

By default, this property is set to ScientificNotation.

This property was introduced in Qt 4.3.

Access functions:

Notation | notation() const
void | setNotation(Notation)

Notifier signal:

void | notationChanged(QDoubleValidator::Notation notation)

See also Notation.

### top : double

This property holds the validator's maximum acceptable value

By default, this property contains a value of infinity.

Access functions:

double | top() const
void | setTop(double)

Notifier signal:

void | topChanged(double top)

See also setRange().

## Member Function Documentation

### QDoubleValidator::QDoubleValidator(double bottom, double top, int decimals, QObject *parent = nullptr)

Constructs a validator object with a parent object. This validator will accept doubles from bottom to top inclusive, with up to decimals digits after the decimal point.

### QDoubleValidator::QDoubleValidator(QObject *parent = nullptr)

Constructs a validator object with a parent object that accepts any double.

### `[virtual]` QDoubleValidator::~QDoubleValidator()

Destroys the validator.

### `[virtual]` void QDoubleValidator::setRange(double minimum, double maximum, int decimals = 0)

Sets the validator to accept doubles from minimum to maximum inclusive, with at most decimals digits after the decimal point.

### `[override virtual]` QValidator::State QDoubleValidator::validate(QString &input, int &pos) const

Reimplements: QValidator::validate(QString &input, int &pos) const.

Returns Acceptable if the string input contains a double that is within the valid range and is in the correct format.

Returns Intermediate if input contains a double that is outside the range or is in the wrong format; e.g. is empty.

Returns Invalid if the input is not a double or with too many digits after the decimal point.

Note: If the valid range consists of just positive doubles (e.g. 0.0 to 100.0) and input is a negative double then Invalid is returned. If notation() is set to StandardNotation, and the input contains more digits before the decimal point than a double in the valid range may have, Invalid is returned. If notation() is ScientificNotation, and the input is not in the valid range, Intermediate is returned. The value may yet become valid by changing the exponent.

By default, the pos parameter is not used by this validator.