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QJSPrimitiveValue Class

The QJSPrimitiveValue class operates on primitive types in JavaScript semantics. 更多...

头： #include <QJSPrimitiveValue>
CMake: find_package(Qt6 REQUIRED COMPONENTS Qml)
target_link_libraries(mytarget PRIVATE Qt6::Qml)
qmake: QT += qml
Since: Qt 6.1

公共类型

enum Type { Undefined, Null, Boolean, Integer, Double, String }

公共函数

QJSPrimitiveValue ()
QJSPrimitiveValue (QJSPrimitiveUndefined undefined )
QJSPrimitiveValue (QJSPrimitiveNull null )
QJSPrimitiveValue (bool value )
QJSPrimitiveValue (int value )
QJSPrimitiveValue (double value )
QJSPrimitiveValue (QString value )
QJSPrimitiveValue (const QVariant & value )
QJSPrimitiveValue (QMetaType type , const void * value )
bool 等于 (const QJSPrimitiveValue & other ) const
bool strictlyEquals (const QJSPrimitiveValue & other ) const
bool toBoolean () const
double toDouble () const
int toInteger () const
QString toString () const
QJSPrimitiveValue::Type type () const
bool operator!= (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
QJSPrimitiveValue operator* (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
QJSPrimitiveValue operator+ (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
QJSPrimitiveValue operator- (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
QJSPrimitiveValue operator/ (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
bool operator< (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
bool operator<= (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
bool operator== (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
bool operator> (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )
bool operator>= (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

详细描述

QJSPrimitiveValue supports most of the primitive types defined in the ECMA-262 standard, in particular Undefined, Boolean, Number, and String. Additionally, you can store a JavaScript null in a QJSPrimitiveValue and as a special case of Number, you can store an integer value.

All those values are stored immediately, without interacting with the JavaScript heap. Therefore, you can pass QJSPrimitiveValues between different JavaScript engines. In contrast to QJSManagedValue , there is also no danger in destroying a QJSPrimitiveValue from a different thread than it was created in. On the flip side, QJSPrimitiveValue does not hold a reference to any JavaScript engine.

QJSPrimitiveValue implements the JavaScript arithmetic and comparison operators on the supported types in JavaScript semantics. Types are coerced like the JavaScript engine would coerce them if the operators were written in a JavaScript expression.

The JavaScript Symbol type is not supported as it is of very limited utility regarding arithmetic and comparison operators, the main purpose of QJSPrimitiveValue. In particular, it causes an exception whenever you try to coerce it to a number or a string, and we cannot throw exceptions without a JavaScript Engine.

成员类型文档编制

enum QJSPrimitiveValue:: Type

This enum speicifies the types a QJSPrimitiveValue might contain.

常量 值 描述
QJSPrimitiveValue::Undefined 0 The JavaScript Undefined value.
QJSPrimitiveValue::Null 1 The JavaScript null value. This is in fact not a separate JavaScript type but a special value of the Object type. As it is very common and storable without JavaScript engine, it is still supported.
QJSPrimitiveValue::Boolean 2 A JavaScript Boolean value.
QJSPrimitiveValue::Integer 3 An integer. This is a special case of the JavaScript Number type. JavaScript does not have an actual integer type, but the ECMA-262 standard contains rules on how to transform a Number in order to prepare it for certain operators that only make sense on integers, in particular the bit shift operators. QJSPrimitiveValue 's Integer type represents the result of such a transformation.
QJSPrimitiveValue::Double 4 A JavaScript Number value.
QJSPrimitiveValue::String 5 A JavaScript String value.

成员函数文档编制

QJSPrimitiveValue:: QJSPrimitiveValue ()

Creates a QJSPrimitiveValue of type Undefined.

QJSPrimitiveValue:: QJSPrimitiveValue ( QJSPrimitiveUndefined undefined )

Creates a QJSPrimitiveValue of value undefined and type Undefined.

QJSPrimitiveValue:: QJSPrimitiveValue ( QJSPrimitiveNull null )

Creates a QJSPrimitiveValue of value null and type Null.

QJSPrimitiveValue:: QJSPrimitiveValue ( bool value )

Creates a QJSPrimitiveValue of value value and type Boolean.

QJSPrimitiveValue:: QJSPrimitiveValue ( int value )

Creates a QJSPrimitiveValue of value value and type Integer.

QJSPrimitiveValue:: QJSPrimitiveValue ( double value )

Creates a QJSPrimitiveValue of value value and type Double.

QJSPrimitiveValue:: QJSPrimitiveValue ( QString value )

Creates a QJSPrimitiveValue of value value and type String.

[explicit] QJSPrimitiveValue:: QJSPrimitiveValue (const QVariant & value )

Creates a QJSPrimitiveValue from the contents of value if those contents can be stored in QJSPrimtiveValue. Otherwise this results in a QJSPrimitiveValue of type Undefined.

[default, since 6.4] QJSPrimitiveValue:: QJSPrimitiveValue ( QMetaType type , const void * value )

Creates a QJSPrimitiveValue of type type , and initializes with value if type can be stored in QJSPrimtiveValue. value must not be nullptr in that case. If type cannot be stored this results in a QJSPrimitiveValue of type Undefined.

Note that you have to pass the address of the variable you want stored.

Usually, you never have to use this constructor, use the one taking QVariant 代替。

该函数在 Qt 6.4 引入。

[constexpr] bool QJSPrimitiveValue:: 等于 (const QJSPrimitiveValue & other ) const

Performs the JavaScript '==' operation on this QJSPrimitiveValue and other , and returns the result.

[constexpr] bool QJSPrimitiveValue:: strictlyEquals (const QJSPrimitiveValue & other ) const

Performs the JavaScript '===' operation on this QJSPrimitiveValue and other , and returns the result.

[constexpr] bool QJSPrimitiveValue:: toBoolean () const

Returns the value coerced a boolean by JavaScript rules.

[constexpr] double QJSPrimitiveValue:: toDouble () const

Returns the value coerced to a JavaScript Number by JavaScript rules.

[constexpr] int QJSPrimitiveValue:: toInteger () const

Returns the value coerced to an integral 32bit number by the rules JavaScript would apply when preparing it for a bit shift operation.

QString QJSPrimitiveValue:: toString () const

Returns the value coerced to a JavaScript String by JavaScript rules.

[constexpr] QJSPrimitiveValue::Type QJSPrimitiveValue:: type () const

Returns the type of the QJSPrimitiveValue .

相关非成员

[constexpr, since 6.1] bool operator!= (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '!==' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[since 6.1] QJSPrimitiveValue operator* (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '*' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[since 6.1] QJSPrimitiveValue operator+ (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Perfoms the JavaScript '+' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[since 6.1] QJSPrimitiveValue operator- (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '-' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[since 6.1] QJSPrimitiveValue operator/ (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '/' operation between lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[constexpr, since 6.1] bool operator< (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '<' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[constexpr, since 6.1] bool operator<= (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '<=' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[constexpr, since 6.1] bool operator== (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '===' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[constexpr, since 6.1] bool operator> (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '>' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

[constexpr, since 6.1] bool operator>= (const QJSPrimitiveValue & lhs , const QJSPrimitiveValue & rhs )

Performs the JavaScript '>=' operation on lhs and rhs , and returns the result.

该函数在 Qt 6.1 引入。

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