QJSValue Class

The QJSValue class acts as a container for Qt/JavaScript data types. 更多...

头：	#include <QJSValue>
qmake:	QT += qml
Since:	Qt 5.0

该类在 Qt 5.0 引入。

公共类型

enum	ErrorType { GenericError, RangeError, ReferenceError, SyntaxError, TypeError, URIError }
enum	SpecialValue { UndefinedValue, NullValue }

公共函数

	QJSValue (const char * value )
	QJSValue (const QLatin1String & value )
	QJSValue (const QString & value )
	QJSValue (double value )
	QJSValue (uint value )
	QJSValue (int value )
	QJSValue (bool value )
	QJSValue (QJSValue && other )
	QJSValue (const QJSValue & other )
	QJSValue (QJSValue::SpecialValue value = UndefinedValue)
QJSValue &	operator= (const QJSValue & other )
QJSValue &	operator= (QJSValue && other )
	~QJSValue ()
QJSValue	call (const QJSValueList & args = QJSValueList())
QJSValue	callAsConstructor (const QJSValueList & args = QJSValueList())
QJSValue	callWithInstance (const QJSValue & 实例 , const QJSValueList & args = QJSValueList())
bool	deleteProperty (const QString & name )
bool	等于 (const QJSValue & other ) const
QJSValue::ErrorType	errorType () const
bool	hasOwnProperty (const QString & name ) const
bool	hasProperty (const QString & name ) const
bool	isArray () const
bool	isBool () const
bool	isCallable () const
bool	isDate () const
bool	isError () const
bool	isNull () const
bool	isNumber () const
bool	isObject () const
bool	isQMetaObject () const
bool	isQObject () const
bool	isRegExp () const
bool	isString () const
bool	isUndefined () const
bool	isVariant () const
QJSValue	property (const QString & name ) const
QJSValue	property (quint32 arrayIndex ) const
QJSValue	prototype () const
void	setProperty (const QString & name , const QJSValue & value )
void	setProperty (quint32 arrayIndex , const QJSValue & value )
void	setPrototype (const QJSValue & prototype )
bool	strictlyEquals (const QJSValue & other ) const
bool	toBool () const
QDateTime	toDateTime () const
qint32	toInt () const
double	toNumber () const
const QMetaObject *	toQMetaObject () const
QObject *	toQObject () const
QString	toString () const
quint32	toUInt () const
QVariant	toVariant () const

typedef

QJSValueList

详细描述

QJSValue supports the types defined in the ECMA-262 standard: The primitive types, which are Undefined, Null, Boolean, Number, and String; and the Object and Array types. Additionally, built-in support is provided for Qt/C++ types such as QVariant and QObject .

For the object-based types (including Date and RegExp), use the newT() functions in QJSEngine (如 QJSEngine::newObject ()) to create a QJSValue of the desired type. For the primitive types, use one of the QJSValue constructor overloads. For other types, e.g. registered gadget types such as QPoint , you can use QJSEngine::toScriptValue .

The methods named isT() (e.g. isBool (), isUndefined ()) can be used to test if a value is of a certain type. The methods named toT() (e.g. toBool (), toString ()) can be used to convert a QJSValue to another type. You can also use the generic qjsvalue_cast() function.

Object values have zero or more properties which are themselves QJSValues. Use setProperty () to set a property of an object, and call property () to retrieve the value of a property.

QJSEngine myEngine;
QJSValue myObject = myEngine.newObject();
QJSValue myOtherObject = myEngine.newObject();
myObject.setProperty("myChild", myOtherObject);
myObject.setProperty("name", "John Doe");

If you want to iterate over the properties of a script object, use the QJSValueIterator 类。

Object values have an internal prototype property, which can be accessed with prototype () 和 setPrototype ().

Function objects (objects for which isCallable ()) returns true) can be invoked by calling call (). Constructor functions can be used to construct new objects by calling callAsConstructor ().

使用等于 () 或 strictlyEquals () to compare a QJSValue to another.

Note that a QJSValue for which isObject () is true only carries a reference to an actual object; copying the QJSValue will only copy the object reference, not the object itself. If you want to clone an object (i.e. copy an object's properties to another object), you can do so with the help of a for-in statement in script code, or QJSValueIterator in C++.

Working With Arrays

To create an array using QJSValue, use QJSEngine::newArray ():

// Assumes that this class was declared in QML.
QJSValue jsArray = engine->newArray(3);

To set individual elements in the array, use the setProperty(quint32 arrayIndex, const QJSValue &value) overload. For example, to fill the array above with integers:

for (int i = 0; i < 3; ++i) {
    jsArray.setProperty(i, QRandomGenerator::global().generate());
}

To determine the length of the array, access the "length" property. To access array elements, use the property (quint32 arrayIndex) overload. The following code reads the array we created above back into a list:

QVector<int> integers;
const int length = jsArray.property("length").toInt();
for (int i = 0; i < length; ++i) {
    integers.append(jsArray.property(i).toInt());
}

另请参阅 QJSEngine and QJSValueIterator .

成员类型文档编制

enum QJSValue:: ErrorType

Use this enum for JavaScript language-specific types of Error objects.

They may be useful when emulating language features in C++ requires the use of specialized exception types. In addition, they may help to more clearly communicate certain typical conditions, instead of throwing a generic JavaScript exception. For example, code that deals with networking and resource locators may find it useful to propagate errors related to malformed locators using the URIError type.

常量	值	描述
`QJSValue::GenericError`	`1`	A generic Error object, but not of a specific sub-type.
`QJSValue::RangeError`	`3`	A value did not match the expected set or range.
`QJSValue::ReferenceError`	`4`	A non-existing variable referenced.
`QJSValue::SyntaxError`	`5`	An invalid token or sequence of tokens was encountered that does not conform with the syntax of the language.
`QJSValue::TypeError`	`6`	An operand or argument is incompatible with the type expected.
`QJSValue::URIError`	`7`	A URI handling function was used incorrectly or the URI provided is malformed.

该枚举在 Qt 5.12 引入或被修改。

enum QJSValue:: SpecialValue

This enum is used to specify a single-valued type.

常量	值	描述
`QJSValue::UndefinedValue`	`1`	An undefined value.
`QJSValue::NullValue`	`0`	A null value.

成员函数文档编制

QJSValue:: QJSValue (const char * value )

Constructs a new QJSValue with a string value .

QJSValue:: QJSValue (const QLatin1String & value )

Constructs a new QJSValue with a string value .

QJSValue:: QJSValue (const QString & value )

Constructs a new QJSValue with a string value .

QJSValue:: QJSValue ( double value )

Constructs a new QJSValue with a number value .

QJSValue:: QJSValue ( uint value )

Constructs a new QJSValue with a number value .

QJSValue:: QJSValue ( int value )

Constructs a new QJSValue with a number value .

QJSValue:: QJSValue ( bool value )

Constructs a new QJSValue with a boolean value .

QJSValue:: QJSValue ( QJSValue && other )

Move constructor. Moves from other into this QJSValue object.

QJSValue:: QJSValue (const QJSValue & other )

Constructs a new QJSValue that is a copy of other .

注意，若 other is an object (i.e., isObject () would return true), then only a reference to the underlying object is copied into the new script value (i.e., the object itself is not copied).

QJSValue:: QJSValue ( QJSValue::SpecialValue value = UndefinedValue)

Constructs a new QJSValue with a special value .

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

赋值 other value to this QJSValue .

注意，若 other is an object ( isObject () returns true), only a reference to the underlying object will be assigned; the object itself will not be copied.

QJSValue &QJSValue:: operator= ( QJSValue && other )

移动赋值 other 到此 QJSValue 对象。

QJSValue:: ~QJSValue ()

销毁此 QJSValue .

QJSValue QJSValue:: call (const QJSValueList & args = QJSValueList())

Calls this QJSValue as a function, passing args as arguments to the function, and using the globalObject() as the "this"-object. Returns the value returned from the function.

若此 QJSValue is not callable, call() does nothing and returns an undefined QJSValue .

Calling call() can cause an exception to occur in the script engine; in that case, call() returns the value that was thrown (typically an Error object). You can call isError () on the return value to determine whether an exception occurred.

另请参阅 isCallable (), callWithInstance ()，和 callAsConstructor ().

QJSValue QJSValue:: callAsConstructor (const QJSValueList & args = QJSValueList())

创建新的 对象 and calls this QJSValue as a constructor, using the created object as the `this' object and passing args as arguments. If the return value from the constructor call is an object, then that object is returned; otherwise the default constructed object is returned.

若此 QJSValue is not a function, callAsConstructor() does nothing and returns an undefined QJSValue .

Calling this function can cause an exception to occur in the script engine; in that case, the value that was thrown (typically an Error object) is returned. You can call isError () on the return value to determine whether an exception occurred.

另请参阅 call () 和 QJSEngine::newObject ().

QJSValue QJSValue:: callWithInstance (const QJSValue & 实例 , const QJSValueList & args = QJSValueList())

Calls this QJSValue as a function, using 实例 as the `this' object in the function call, and passing args as arguments to the function. Returns the value returned from the function.

若此 QJSValue is not a function, call () does nothing and returns an undefined QJSValue .

注意，若实例 is not an object, the global object (see QJSEngine::globalObject ()) will be used as the `this' object.

调用 call () can cause an exception to occur in the script engine; in that case, call () returns the value that was thrown (typically an Error object). You can call isError () on the return value to determine whether an exception occurred.

另请参阅 call ().

bool QJSValue:: deleteProperty (const QString & name )

Attempts to delete this object's property of the given name . Returns true if the property was deleted, otherwise returns false.

The behavior of this function is consistent with the JavaScript delete operator. In particular:

Non-configurable properties cannot be deleted.
This function will return true even if this object doesn't have a property of the given name (i.e., non-existent properties are "trivially deletable").
If this object doesn't have an own property of the given name , but an object in the prototype () chain does, the prototype object's property is not deleted, and this function returns true.

另请参阅 setProperty () 和 hasOwnProperty ().

bool QJSValue:: 等于 (const QJSValue & other ) const

返回 true，若此 QJSValue 等于 other , otherwise returns false. The comparison follows the behavior described in ECMA-262 section 11.9.3, "The Abstract Equality Comparison Algorithm".

This function can return true even if the type of this QJSValue is different from the type of the other value; i.e. the comparison is not strict. For example, comparing the number 9 to the string "9" returns true; comparing an undefined value to a null value returns true; comparing a Number object whose primitive value is 6 to a 字符串 object whose primitive value is "6" returns true; and comparing the number 1 to the boolean value true returns true. If you want to perform a comparison without such implicit value conversion, use strictlyEquals ().

Note that if this QJSValue 或 other value are objects, calling this function has side effects on the script engine, since the engine will call the object's valueOf() function (and possibly toString ()) in an attempt to convert the object to a primitive value (possibly resulting in an uncaught script exception).

另请参阅 strictlyEquals ().

QJSValue::ErrorType QJSValue:: errorType () const

Returns the error type this QJSValue represents if it is an Error object. Otherwise, returns NoError."

该函数在 Qt 5.12 引入。

另请参阅 isError () 和 QJSEngine - Script Exceptions .

bool QJSValue:: hasOwnProperty (const QString & name ) const

Returns true if this object has an own (not prototype-inherited) property of the given name ，否则返回 false。

另请参阅 property () 和 hasProperty ().

bool QJSValue:: hasProperty (const QString & name ) const

Returns true if this object has a property of the given name ，否则返回 false。

另请参阅 property () 和 hasOwnProperty ().

bool QJSValue:: isArray () const

返回 true，若此 QJSValue is an object of the Array class; otherwise returns false.

另请参阅 QJSEngine::newArray ().

bool QJSValue:: isBool () const

返回 true，若此 QJSValue is of the primitive type Boolean; otherwise returns false.

另请参阅 toBool ().

bool QJSValue:: isCallable () const

返回 true，若此 QJSValue is a function, otherwise returns false.

另请参阅 call ().

bool QJSValue:: isDate () const

返回 true，若此 QJSValue is an object of the Date class; otherwise returns false.

bool QJSValue:: isError () const

返回 true，若此 QJSValue is an object of the Error class; otherwise returns false.

另请参阅 errorType () 和 QJSEngine - Script Exceptions .

bool QJSValue:: isNull () const

返回 true，若此 QJSValue is of the primitive type Null; otherwise returns false.

bool QJSValue:: isNumber () const

返回 true，若此 QJSValue is of the primitive type Number; otherwise returns false.

另请参阅 toNumber ().

bool QJSValue:: isObject () const

返回 true，若此 QJSValue is of the Object type; otherwise returns false.

Note that function values, variant values, and QObject values are objects, so this function returns true for such values.

另请参阅 QJSEngine::newObject ().

bool QJSValue:: isQMetaObject () const

返回 true，若此 QJSValue 是 QMetaObject ；否则返回 false。

该函数在 Qt 5.8 引入。

另请参阅 toQMetaObject () 和 QJSEngine::newQMetaObject ().

bool QJSValue:: isQObject () const

返回 true，若此 QJSValue 是 QObject ；否则返回 false。

Note: This function returns true even if the QObject that this QJSValue wraps has been deleted.

另请参阅 toQObject () 和 QJSEngine::newQObject ().

bool QJSValue:: isRegExp () const

返回 true，若此 QJSValue is an object of the RegExp class; otherwise returns false.

bool QJSValue:: isString () const

返回 true，若此 QJSValue is of the primitive type String; otherwise returns false.

另请参阅 toString ().

bool QJSValue:: isUndefined () const

返回 true，若此 QJSValue is of the primitive type Undefined; otherwise returns false.

bool QJSValue:: isVariant () const

返回 true，若此 QJSValue is a variant value; otherwise returns false.

另请参阅 toVariant ().

QJSValue QJSValue:: property (const QString & name ) const

Returns the value of this QJSValue 's property with the given name . If no such property exists, an undefined QJSValue 被返回。

If the property is implemented using a getter function (i.e. has the PropertyGetter flag set), calling property() has side-effects on the script engine, since the getter function will be called (possibly resulting in an uncaught script exception). If an exception occurred, property() returns the value that was thrown (typically an Error 对象)。

To access array elements, use the setProperty(quint32 arrayIndex, const QJSValue &value) overload instead.

另请参阅 setProperty (), hasProperty ()，和 QJSValueIterator .

QJSValue QJSValue:: property ( quint32 arrayIndex ) const

这是重载函数。

Returns the property at the given arrayIndex .

It is possible to access elements in an array in two ways. The first is to use the array index as the property name:

qDebug() << jsValueArray.property(QLatin1String("4")).toString();

The second is to use the overload that takes an index:

qDebug() << jsValueArray.property(4).toString();

Both of these approaches achieve the same result, except that the latter:

Is easier to use (can use an integer directly)
Is faster (no conversion to integer)

若此 QJSValue is not an Array object, this function behaves as if property() was called with the string representation of arrayIndex .

QJSValue QJSValue:: prototype () const

若此 QJSValue is an object, returns the internal prototype ( __proto__ property) of this object; otherwise returns an undefined QJSValue .

另请参阅 setPrototype () 和 isObject ().

void QJSValue:: setProperty (const QString & name , const QJSValue & value )

Sets the value of this QJSValue 's property with the given name 到给定 value .

若此 QJSValue is not an object, this function does nothing.

若此 QJSValue does not already have a property with name name , a new property is created.

To modify array elements, use the setProperty(quint32 arrayIndex, const QJSValue &value) overload instead.

另请参阅 property () 和 deleteProperty ().

void QJSValue:: setProperty ( quint32 arrayIndex , const QJSValue & value )

这是重载函数。

Sets the property at the given arrayIndex 到给定 value .

It is possible to modify elements in an array in two ways. The first is to use the array index as the property name:

jsValueArray.setProperty(QLatin1String("4"), value);

The second is to use the overload that takes an index:

jsValueArray.setProperty(4, value);

Both of these approaches achieve the same result, except that the latter:

Is easier to use (can use an integer directly)
Is faster (no conversion to integer)

若此 QJSValue is not an Array object, this function behaves as if setProperty() was called with the string representation of arrayIndex .

另请参阅 property (quint32 arrayIndex) and Working With Arrays .

void QJSValue:: setPrototype (const QJSValue & prototype )

若此 QJSValue is an object, sets the internal prototype ( __proto__ property) of this object to be prototype ; if the QJSValue is null, it sets the prototype to null; otherwise does nothing.

The internal prototype should not be confused with the public property with name "prototype"; the public prototype is usually only set on functions that act as constructors.

另请参阅 prototype () 和 isObject ().

bool QJSValue:: strictlyEquals (const QJSValue & other ) const

返回 true，若此 QJSValue 等于 other using strict comparison (no conversion), otherwise returns false. The comparison follows the behavior described in ECMA-262 section 11.9.6, "The Strict Equality Comparison Algorithm".

If the type of this QJSValue is different from the type of the other value, this function returns false. If the types are equal, the result depends on the type, as shown in the following table:

类型	结果
Undefined	true
Null	true
布尔	true if both values are true, false otherwise
Number	false if either value is NaN (Not-a-Number); true if values are equal, false otherwise
字符串	true if both values are exactly the same sequence of characters, false otherwise
对象	true if both values refer to the same object, false otherwise

另请参阅 等于 ().

bool QJSValue:: toBool () const

Returns the boolean value of this QJSValue , using the conversion rules described in ECMA-262 section 9.2, "ToBoolean".

Note that if this QJSValue is an object, calling this function has side effects on the script engine, since the engine will call the object's valueOf() function (and possibly toString ()) in an attempt to convert the object to a primitive value (possibly resulting in an uncaught script exception).

另请参阅 isBool ().

QDateTime QJSValue:: toDateTime () const

返回 QDateTime representation of this value, in local time. If this QJSValue is not a date, or the value of the date is NaN (Not-a-Number), an invalid QDateTime 被返回。

另请参阅 isDate ().

qint32 QJSValue:: toInt () const

Returns the signed 32-bit integer value of this QJSValue , using the conversion rules described in ECMA-262 section 9.5, "ToInt32".

另请参阅 toNumber () 和 toUInt ().

double QJSValue:: toNumber () const

Returns the number value of this QJSValue , as defined in ECMA-262 section 9.3, "ToNumber".

另请参阅 isNumber (), toInt ()，和 toUInt ().

const QMetaObject *QJSValue:: toQMetaObject () const

* If this QJSValue 是 QMetaObject , returns the QMetaObject pointer * that the QJSValue represents; otherwise, returns nullptr . * *

该函数在 Qt 5.8 引入。

另请参阅 isQMetaObject ().

QObject *QJSValue:: toQObject () const

若此 QJSValue 是 QObject , returns the QObject pointer that the QJSValue represents; otherwise, returns nullptr .

若 QObject that this QJSValue wraps has been deleted, this function returns nullptr (i.e. it is possible for toQObject() to return nullptr even when isQObject () 返回 true)。

另请参阅 isQObject ().

QString QJSValue:: toString () const

Returns the string value of this QJSValue , as defined in ECMA-262 section 9.8, "ToString".

Note that if this QJSValue is an object, calling this function has side effects on the script engine, since the engine will call the object's toString() function (and possibly valueOf()) in an attempt to convert the object to a primitive value (possibly resulting in an uncaught script exception).

另请参阅 isString ().

quint32 QJSValue:: toUInt () const

Returns the unsigned 32-bit integer value of this QJSValue , using the conversion rules described in ECMA-262 section 9.6, "ToUint32".

另请参阅 toNumber () 和 toInt ().

QVariant QJSValue:: toVariant () const

返回 QVariant value of this QJSValue , if it can be converted to a QVariant ；否则返回无效 QVariant . The conversion is performed according to the following table:

Input Type	结果
Undefined	An invalid QVariant .
Null	A QVariant containing a null pointer ( QMetaType::Nullptr ).
布尔	A QVariant containing the value of the boolean.
Number	A QVariant containing the value of the number.
字符串	A QVariant containing the value of the string.
QVariant 对象	The result is the QVariant value of the object (no conversion).
QObject 对象	A QVariant containing a pointer to the QObject .
Date Object	A QVariant containing the date value ( toDateTime ()).
RegExp Object	A QVariant containing the regular expression value.
Array Object	The array is converted to a QVariantList . Each element is converted to a QVariant , recursively; cyclic references are not followed.
对象	The object is converted to a QVariantMap . Each property is converted to a QVariant , recursively; cyclic references are not followed.

另请参阅 isVariant ().

QJSValue Class

公共类型

公共函数

相关非成员

详细描述

Working With Arrays

成员类型文档编制

enum QJSValue:: ErrorType

enum QJSValue:: SpecialValue

成员函数文档编制

QJSValue:: QJSValue (const char * value )

QJSValue:: QJSValue (const QLatin1String & value )

QJSValue:: QJSValue (const QString & value )

QJSValue:: QJSValue ( double value )

QJSValue:: QJSValue ( uint value )

QJSValue:: QJSValue ( int value )

QJSValue:: QJSValue ( bool value )

QJSValue:: QJSValue ( QJSValue && other )

QJSValue:: QJSValue (const QJSValue & other )

QJSValue:: QJSValue ( QJSValue::SpecialValue value = UndefinedValue)

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

QJSValue &QJSValue:: operator= ( QJSValue && other )

QJSValue:: ~QJSValue ()

QJSValue QJSValue:: call (const QJSValueList & args = QJSValueList())

QJSValue QJSValue:: callAsConstructor (const QJSValueList & args = QJSValueList())

QJSValue QJSValue:: callWithInstance (const QJSValue & 实例 , const QJSValueList & args = QJSValueList())

bool QJSValue:: deleteProperty (const QString & name )

bool QJSValue:: 等于 (const QJSValue & other ) const

QJSValue::ErrorType QJSValue:: errorType () const

bool QJSValue:: hasOwnProperty (const QString & name ) const

bool QJSValue:: hasProperty (const QString & name ) const

bool QJSValue:: isArray () const

bool QJSValue:: isBool () const

bool QJSValue:: isCallable () const

bool QJSValue:: isDate () const

bool QJSValue:: isError () const

bool QJSValue:: isNull () const

bool QJSValue:: isNumber () const

bool QJSValue:: isObject () const

bool QJSValue:: isQMetaObject () const

bool QJSValue:: isQObject () const

bool QJSValue:: isRegExp () const

bool QJSValue:: isString () const

bool QJSValue:: isUndefined () const

bool QJSValue:: isVariant () const

QJSValue QJSValue:: property (const QString & name ) const

QJSValue QJSValue:: property ( quint32 arrayIndex ) const

QJSValue QJSValue:: prototype () const

void QJSValue:: setProperty (const QString & name , const QJSValue & value )

void QJSValue:: setProperty ( quint32 arrayIndex , const QJSValue & value )

void QJSValue:: setPrototype (const QJSValue & prototype )

bool QJSValue:: strictlyEquals (const QJSValue & other ) const

bool QJSValue:: toBool () const

QDateTime QJSValue:: toDateTime () const

qint32 QJSValue:: toInt () const

double QJSValue:: toNumber () const

const QMetaObject *QJSValue:: toQMetaObject () const

QObject *QJSValue:: toQObject () const

QString QJSValue:: toString () const

quint32 QJSValue:: toUInt () const

QVariant QJSValue:: toVariant () const

相关非成员

typedef QJSValueList

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