Qt 5.6 | Qt Core | C++ Classes | QMetaProperty

Qt 5.6.2 Reference Documentation

# QMetaProperty Class

The QMetaProperty class provides meta-data about a property. More...

Header: | #include <QMetaProperty>
qmake: | QT += core

- List of all members, including inherited members
- Obsolete members

## Public Functions

QMetaEnum | enumerator() const
bool | hasNotifySignal() const
bool | isConstant() const
bool | isDesignable(const QObject *object = Q_NULLPTR) const
bool | isEnumType() const
bool | isFinal() const
bool | isFlagType() const
bool | isReadable() const
bool | isResettable() const
bool | isScriptable(const QObject *object = Q_NULLPTR) const
bool | isStored(const QObject *object = Q_NULLPTR) const
bool | isUser(const QObject *object = Q_NULLPTR) const
bool | isValid() const
bool | isWritable() const
const char * | name() const
QMetaMethod | notifySignal() const
int | notifySignalIndex() const
int | propertyIndex() const
QVariant | read(const QObject *object) const
QVariant | readOnGadget(const void *gadget) const
bool | reset(QObject *object) const
bool | resetOnGadget(void *gadget) const
int | revision() const
QVariant::Type | type() const
const char * | typeName() const
int | userType() const
bool | write(QObject *object, const QVariant &value) const
bool | writeOnGadget(void *gadget, const QVariant &value) const

## Detailed Description

The QMetaProperty class provides meta-data about a property.

Property meta-data is obtained from an object's meta-object. See QMetaObject::property() and QMetaObject::propertyCount() for details.

### Property Meta-Data

A property has a name() and a type(), as well as various attributes that specify its behavior: isReadable(), isWritable(), isDesignable(), isScriptable(), revision(), and isStored().

If the property is an enumeration, isEnumType() returns `true`; if the property is an enumeration that is also a flag (i.e. its values can be combined using the OR operator), isEnumType() and isFlagType() both return true. The enumerator for these types is available from enumerator().

The property's values are set and retrieved with read(), write(), and reset(); they can also be changed through QObject's set and get functions. See QObject::setProperty() and QObject::property() for details.

### Copying and Assignment

QMetaProperty objects can be copied by value. However, each copy will refer to the same underlying property meta-data.

See also QMetaObject, QMetaEnum, QMetaMethod, and Qt's Property System.

## Member Function Documentation

### QMetaEnum QMetaProperty::enumerator() const

Returns the enumerator if this property's type is an enumerator type; otherwise the returned value is undefined.

See also isEnumType() and isFlagType().

### bool QMetaProperty::hasNotifySignal() const

Returns `true` if this property has a corresponding change notify signal; otherwise returns `false`.

See also notifySignal().

### bool QMetaProperty::isConstant() const

Returns `true` if the property is constant; otherwise returns `false`.

A property is constant if the `Q_PROPERTY()`'s `CONSTANT` attribute is set.

This function was introduced in Qt 4.6.

### bool QMetaProperty::isDesignable(const QObject *object = Q_NULLPTR) const

Returns `true` if this property is designable for the given object; otherwise returns `false`.

If no object is given, the function returns `false` if the `Q_PROPERTY()`'s `DESIGNABLE` attribute is false; otherwise returns `true` (if the attribute is true or is a function or expression).

See also isScriptable() and isStored().

### bool QMetaProperty::isEnumType() const

Returns `true` if the property's type is an enumeration value; otherwise returns `false`.

See also enumerator() and isFlagType().

### bool QMetaProperty::isFinal() const

Returns `true` if the property is final; otherwise returns `false`.

A property is final if the `Q_PROPERTY()`'s `FINAL` attribute is set.

This function was introduced in Qt 4.6.

### bool QMetaProperty::isFlagType() const

Returns `true` if the property's type is an enumeration value that is used as a flag; otherwise returns `false`.

Flags can be combined using the OR operator. A flag type is implicitly also an enum type.

See also isEnumType(), enumerator(), and QMetaEnum::isFlag().

### bool QMetaProperty::isReadable() const

Returns `true` if this property is readable; otherwise returns `false`.

See also isWritable(), read(), and isValid().

### bool QMetaProperty::isResettable() const

Returns `true` if this property can be reset to a default value; otherwise returns `false`.

See also reset().

### bool QMetaProperty::isScriptable(const QObject *object = Q_NULLPTR) const

Returns `true` if the property is scriptable for the given object; otherwise returns `false`.

If no object is given, the function returns `false` if the `Q_PROPERTY()`'s `SCRIPTABLE` attribute is false; otherwise returns true (if the attribute is true or is a function or expression).

See also isDesignable() and isStored().

### bool QMetaProperty::isStored(const QObject *object = Q_NULLPTR) const

Returns `true` if the property is stored for object; otherwise returns false.

If no object is given, the function returns `false` if the `Q_PROPERTY()`'s `STORED` attribute is false; otherwise returns true (if the attribute is true or is a function or expression).

See also isDesignable() and isScriptable().

### bool QMetaProperty::isUser(const QObject *object = Q_NULLPTR) const

Returns `true` if this property is designated as the `USER` property, i.e., the one that the user can edit for object or that is significant in some other way. Otherwise it returns false. e.g., the `text` property is the `USER` editable property of a QLineEdit.

If object is null, the function returns `false` if the `Q_PROPERTY()`'s `USER` attribute is false. Otherwise it returns true.

See also QMetaObject::userProperty(), isDesignable(), and isScriptable().

### bool QMetaProperty::isValid() const

Returns `true` if this property is valid (readable); otherwise returns `false`.

See also isReadable().

### bool QMetaProperty::isWritable() const

Returns `true` if this property is writable; otherwise returns false.

See also isReadable() and write().

### const char *QMetaProperty::name() const

Returns this property's name.

See also type() and typeName().

### QMetaMethod QMetaProperty::notifySignal() const

Returns the QMetaMethod instance of the property change notifying signal if one was specified, otherwise returns an invalid QMetaMethod.

This function was introduced in Qt 4.5.

See also hasNotifySignal().

### int QMetaProperty::notifySignalIndex() const

Returns the index of the property change notifying signal if one was specified, otherwise returns -1.

This function was introduced in Qt 4.6.

See also hasNotifySignal().

### int QMetaProperty::propertyIndex() const

Returns this property's index.

This function was introduced in Qt 4.6.

### QVariant QMetaProperty::read(const QObject *object) const

Reads the property's value from the given object. Returns the value if it was able to read it; otherwise returns an invalid variant.

See also write(), reset(), and isReadable().

### QVariant QMetaProperty::readOnGadget(const void *gadget) const

Reads the property's value from the given gadget. Returns the value if it was able to read it; otherwise returns an invalid variant.

This function should only be used if this is a property of a Q_GADGET

This function was introduced in Qt 5.5.

### bool QMetaProperty::reset(QObject *object) const

Resets the property for the given object with a reset method. Returns `true` if the reset worked; otherwise returns `false`.

Reset methods are optional; only a few properties support them.

See also read() and write().

### bool QMetaProperty::resetOnGadget(void *gadget) const

Resets the property for the given gadget with a reset method. Returns `true` if the reset worked; otherwise returns `false`.

Reset methods are optional; only a few properties support them.

This function should only be used if this is a property of a Q_GADGET

This function was introduced in Qt 5.5.

### int QMetaProperty::revision() const

Returns the property revision if one was specified by REVISION, otherwise returns 0.

This function was introduced in Qt 5.1.

### QVariant::Type QMetaProperty::type() const

Returns this property's type. The return value is one of the values of the QVariant::Type enumeration.

See also userType(), typeName(), and name().

### const char *QMetaProperty::typeName() const

Returns the name of this property's type.

See also type() and name().

### int QMetaProperty::userType() const

Returns this property's user type. The return value is one of the values that are registered with QMetaType, or QMetaType::UnknownType if the type is not registered.

This function was introduced in Qt 4.2.

See also type(), QMetaType, and typeName().

### bool QMetaProperty::write(QObject *object, const QVariant &value) const

Writes value as the property's value to the given object. Returns true if the write succeeded; otherwise returns `false`.

If value is not of the same type type as the property, a conversion is attempted. An empty QVariant() is equivalent to a call to reset() if this property is resetable, or setting a default-constructed object otherwise.

See also read(), reset(), and isWritable().

### bool QMetaProperty::writeOnGadget(void *gadget, const QVariant &value) const

Writes value as the property's value to the given gadget. Returns true if the write succeeded; otherwise returns `false`.

This function should only be used if this is a property of a Q_GADGET

This function was introduced in Qt 5.5.