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QFlags Class Reference

The QFlags class provides a type-safe way of storing OR-combinations of enum values. Далее...

 #include <QFlags>

• Список всех членов, включая унаследованные

Открытые типы

Открытые функции

Макросы

Подробное описание

The QFlags class provides a type-safe way of storing OR-combinations of enum values.

The QFlags<Enum> class is a template class, where Enum is an enum type. QFlags is used throughout Qt for storing combinations of enum values.

The traditional C++ approach for storing OR-combinations of enum values is to use an int or uint variable. The inconvenience with this approach is that there's no type checking at all; any enum value can be OR'd with any other enum value and passed on to a function that takes an int or uint.

Qt uses QFlags to provide type safety. For example, the Qt::Alignment type is simply a typedef for QFlags<Qt::AlignmentFlag>. QLabel::setAlignment() takes a Qt::Alignment parameter, which means that any combination of Qt::AlignmentFlag values,or 0, is legal:

 label->setAlignment(Qt::AlignLeft | Qt::AlignTop);

If you try to pass a value from another enum or just a plain integer other than 0, the compiler will report an error. If you need to cast integer values to flags in a untyped fashion, you can use the explicit QFlags constructor as cast operator.

If you want to use QFlags for your own enum types, use the Q_DECLARE_FLAGS() and Q_DECLARE_OPERATORS_FOR_FLAGS().

Пример:

 class MyClass
 {
 public:
     enum Option {
         NoOptions = 0x0,
         ShowTabs = 0x1,
         ShowAll = 0x2,
         SqueezeBlank = 0x4
     };
     Q_DECLARE_FLAGS(Options, Option)
     ...
 };

 Q_DECLARE_OPERATORS_FOR_FLAGS(MyClass::Options)

You can then use the MyClass::Options type to store combinations of MyClass::Option values.

Flags and the Meta-Object System

The Q_DECLARE_FLAGS() macro does not expose the flags to the meta-object system, so they cannot be used by Qt Script or edited in Qt Designer. To make the flags available for these purposes, the Q_FLAGS() macro must be used:

 Q_FLAGS(Options)

Naming Convention

A sensible naming convention for enum types and associated QFlags types is to give a singular name to the enum type (e.g., Option) and a plural name to the QFlags type (e.g., Options). When a singular name is desired for the QFlags type (e.g., Alignment), you can use Flag as the suffix for the enum type (e.g., AlignmentFlag).

See also QFlag.

Описание типов-членов

typedef QFlags::enum_type

Typedef for the Enum template type.

Описание функций-членов

QFlags::QFlags ( const QFlags & other )

Создаёт копию other.

QFlags::QFlags ( Enum flag )

Constructs a QFlags object storing the given flag.

QFlags::QFlags ( Zero zero = 0 )

Constructs a QFlags object with no flags set. zero must be a literal 0 value.

QFlags::QFlags ( QFlag value )

Constructs a QFlags object initialized with the given integer value.

The QFlag type is a helper type. By using it here instead of int, we effectively ensure that arbitrary enum values cannot be cast to a QFlags, whereas untyped enum values (i.e., int values) can.

bool QFlags::testFlag ( Enum flag ) const

Returns true if the flag is set, otherwise false.

Эта функция была введена в Qt 4.2.

QFlags::operator int () const

Returns the value stored in the QFlags object as an integer.

bool QFlags::operator! () const

Returns true if no flag is set (i.e., if the value stored by the QFlags object is 0); otherwise returns false.

QFlags QFlags::operator& ( int mask ) const

Returns a QFlags object containing the result of the bitwise AND operation on this object and mask.

See also operator&=(), operator|(), operator^(), and operator~().

QFlags QFlags::operator& ( uint mask ) const

Это перегруженная функция.

QFlags QFlags::operator& ( Enum mask ) const

Это перегруженная функция.

QFlags & QFlags::operator&= ( int mask )

Performs a bitwise AND operation with mask and stores the result in this QFlags object. Returns a reference to this object.

See also operator&(), operator|=(), and operator^=().

QFlags & QFlags::operator&= ( uint mask )

Это перегруженная функция.

QFlags & QFlags::operator= ( const QFlags & other )

Assigns other to this object and returns a reference to this object.

QFlags QFlags::operator^ ( QFlags other ) const

Returns a QFlags object containing the result of the bitwise XOR operation on this object and other.

See also operator^=(), operator&(), operator|(), and operator~().

QFlags QFlags::operator^ ( Enum other ) const

Это перегруженная функция.

QFlags & QFlags::operator^= ( QFlags other )

Performs a bitwise XOR operation with other and stores the result in this QFlags object. Returns a reference to this object.

See also operator^(), operator&=(), and operator|=().

QFlags & QFlags::operator^= ( Enum other )

Это перегруженная функция.

QFlags QFlags::operator| ( QFlags other ) const

Returns a QFlags object containing the result of the bitwise OR operation on this object and other.

See also operator|=(), operator^(), operator&(), and operator~().

QFlags QFlags::operator| ( Enum other ) const

Это перегруженная функция.

QFlags & QFlags::operator|= ( QFlags other )

Performs a bitwise OR operation with other and stores the result in this QFlags object. Returns a reference to this object.

See also operator|(), operator&=(), and operator^=().

QFlags & QFlags::operator|= ( Enum other )

Это перегруженная функция.

QFlags QFlags::operator~ () const

Returns a QFlags object that contains the bitwise negation of this object.

See also operator&(), operator|(), and operator^().

Описание макросов

Q_DECLARE_FLAGS ( Flags, Enum )

The Q_DECLARE_FLAGS() macro expands to

 typedef QFlags<Enum> Flags;

Enum is the name of an existing enum type, whereas Flags is the name of the QFlags<Enum> typedef.

See the QFlags documentation for details.

See also Q_DECLARE_OPERATORS_FOR_FLAGS().

Q_DECLARE_OPERATORS_FOR_FLAGS ( Flags )

The Q_DECLARE_OPERATORS_FOR_FLAGS() macro declares global operator|() functions for Flags, which is of type QFlags<T>.

See the QFlags documentation for details.

See also Q_DECLARE_FLAGS().