The QFlags class provides a type-safe way of storing OR-combinations of enum values. More...
| Header: | #include <QFlags> |
| qmake: | QT += core |
| QFlags(const QFlags<T> &other) | |
| QFlags(Enum flags) | |
| QFlags(QFlags::Zero = Q_NULLPTR) | |
| QFlags(QFlag flag) | |
| QFlags(int flags) | |
| QFlags<T> & | setFlag(Enum flag, bool on = true) |
| bool | testFlag(Enum flag) const |
| QFlags::Int | operator QFlags::Int() const |
| bool | operator!() const |
| QFlags<T> | operator&(int mask) const |
| QFlags<T> | operator&(uint mask) const |
| QFlags<T> | operator&(Enum other) const |
| QFlags<T> & | operator&=(int mask) |
| QFlags<T> & | operator&=(uint mask) |
| QFlags<T> & | operator&=(Enum mask) |
| QFlags<T> & | operator=(const QFlags<T> &other) |
| QFlags<T> | operator^(QFlags<T> other) const |
| QFlags<T> | operator^(Enum other) const |
| QFlags<T> & | operator^=(QFlags<T> other) |
| QFlags<T> & | operator^=(Enum other) |
| QFlags<T> | operator|(QFlags<T> other) const |
| QFlags<T> | operator|(Enum other) const |
| QFlags<T> & | operator|=(QFlags<T> other) |
| QFlags<T> & | operator|=(Enum other) |
| QFlags<T> | operator~() const |
| Q_DECLARE_FLAGS(Flags, Enum) | |
| Q_DECLARE_OPERATORS_FOR_FLAGS(Flags) |
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().
Example:
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.
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_FLAG() macro must be used:
Q_FLAG(Options)
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.
Typedef for the integer type used for storage as well as for implicit conversion. Either int or unsigned int, depending on whether the enum's underlying type is signed or unsigned.
This typedef was introduced in Qt 5.0.
Typedef for the Enum template type.
Constructs a copy of other.
Constructs a QFlags object storing the flags.
Constructs a QFlags object with no flags set. The parameter must be a literal 0 value.
Constructs a QFlags object initialized with the integer flag.
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.
Constructs a QFlags object initialized with all flags combined using the bitwise OR operator.
This function was introduced in Qt 5.4.
See also operator|=() and operator|().
Sets the flag flag if on is true or unsets it if on is false. Returns a reference to this object.
This function was introduced in Qt 5.7.
Returns true if the flag flag is set, otherwise false.
This function was introduced in Qt 4.2.
Returns the value stored in the QFlags object as an integer.
See also Int.
Returns true if no flag is set (i.e., if the value stored by the QFlags object is 0); otherwise returns false.
Returns a QFlags object containing the result of the bitwise AND operation on this object and mask.
See also operator&=(), operator|(), operator^(), and operator~().
This is an overloaded function.
This is an overloaded function.
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^=().
This is an overloaded function.
This is an overloaded function.
Assigns other to this object and returns a reference to this object.
Returns a QFlags object containing the result of the bitwise XOR operation on this object and other.
See also operator^=(), operator&(), operator|(), and operator~().
This is an overloaded function.
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|=().
This is an overloaded function.
Returns a QFlags object containing the result of the bitwise OR operation on this object and other.
See also operator|=(), operator^(), operator&(), and operator~().
This is an overloaded function.
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^=().
This is an overloaded function.
Returns a QFlags object that contains the bitwise negation of this object.
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().
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().
