QJSValue Class

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

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

公共类型

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

公共函数

QJSValue (QJSValue::SpecialValue value = UndefinedValue)
QJSValue (bool value )
QJSValue (int value )
QJSValue (uint value )
QJSValue (double value )
QJSValue (const QString & value )
QJSValue (const QLatin1String & value )
QJSValue (const char * value )
QJSValue (const QJSValue & other )
QJSValue (QJSValue && other )
~QJSValue ()
QJSValue call (const QJSValueList & args = QJSValueList()) const
QJSValue callAsConstructor (const QJSValueList & args = QJSValueList()) const
QJSValue callWithInstance (const QJSValue & 实例 , const QJSValueList & args = QJSValueList()) const
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 isUrl () 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
QJSPrimitiveValue toPrimitive () const
const QMetaObject * toQMetaObject () const
QObject * toQObject () const
QString toString () const
quint32 toUInt () const
QVariant toVariant (QJSValue::ObjectConversionBehavior behavior ) const
QVariant toVariant () const
QJSValue & operator= (QJSValue && other )
QJSValue & operator= (const QJSValue & other )
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());
}
					

Converting to JSON

It's possible to convert a QJSValue to a JSON type. For example, to convert to an array, use QJSEngine::fromScriptValue ():

const QJsonValue jsonValue = engine.fromScriptValue<QJsonValue>(jsValue);
const QJsonArray jsonArray = jsonValue.toArray();
					

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 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.

enum QJSValue:: ObjectConversionBehavior

This enum is used to specify how JavaScript objects and symbols without an equivalent native Qt type should be treated when converting to QVariant .

常量 描述
QJSValue::ConvertJSObjects 0 A best-effort, possibly lossy, conversion is attempted. Symbols are converted to QString .
QJSValue::RetainJSObjects 1 The value is retained as QJSValue wrapped in QVariant .

enum QJSValue:: SpecialValue

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

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

成员函数文档编制

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

Constructs a new QJSValue with a special value .

QJSValue:: QJSValue ( bool value )

Constructs a new QJSValue with a boolean value .

QJSValue:: QJSValue ( int value )

Constructs a new QJSValue with a number value .

QJSValue:: QJSValue ( uint value )

Constructs a new QJSValue with a number value .

QJSValue:: QJSValue ( double value )

Constructs a new QJSValue with a number value .

QJSValue:: QJSValue (const QString & 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 char * value )

Constructs a new QJSValue with a string value .

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 && other )

Move constructor. Moves from other into this QJSValue object.

[noexcept] QJSValue:: ~QJSValue ()

销毁此 QJSValue .

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

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()) const

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()) const

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 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."

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 QMetaObject ;否则返回 false。

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

bool QJSValue:: isQObject () const

返回 true,若此 QJSValue 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 or if the managed value has been cleared (by deleting the engine). Otherwise returns false.

bool QJSValue:: isUrl () const

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

注意: 对于 QJSValue 包含 QUrl , this function returns false. However, toVariant().value<QUrl>() works in both cases.

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".

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 toNumber () 和 toUInt ().

double QJSValue:: toNumber () const

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

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 isNumber (), toInt (),和 toUInt ().

QJSPrimitiveValue QJSValue:: toPrimitive () const

Converts the value to a QJSPrimitiveValue . If the value holds a type supported by QJSPrimitiveValue , the value is copied. Otherwise the value is converted to a string, and the string is stored in QJSPrimitiveValue .

注意: Conversion of a managed value to a string can throw an exception. In particular, symbols cannot be coerced into strings, or a custom toString () method may throw. In this case the result is the undefined value and the engine carries an error after the conversion.

const QMetaObject *QJSValue:: toQMetaObject () const

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

另请参阅 isQMetaObject ().

QObject *QJSValue:: toQObject () const

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

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".

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 toNumber () 和 toInt ().

QVariant QJSValue:: toVariant ( QJSValue::ObjectConversionBehavior behavior ) const

返回 QVariant value of this QJSValue , if it can be converted to a QVariant ;否则返回无效 QVariant . Some JavaScript types and objects have native expressions in Qt. Those are converted to their native expressions. For example:

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 ()).
RegularExpression 对象 A QVariant containing the regular expression value.

For other types the behavior parameter is relevant. If ConvertJSObjects is given, a best effort but possibly lossy conversion is attempted. Generic JavaScript objects are converted to QVariantMap . JavaScript arrays are converted to QVariantList . Each property or element is converted to a QVariant , recursively; cyclic references are not followed. JavaScript function objects are dropped. If RetainJSObjects is given, the QJSValue is wrapped into a QVariant 凭借 QVariant::fromValue (). The resulting conversion is lossless but the internal structure of the objects is not immediately accessible.

另请参阅 isVariant ().

QVariant QJSValue:: toVariant () const

这是重载函数。

Returns toVariant( ConvertJSObjects ).

另请参阅 isVariant ().

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

移动赋值 other 到此 QJSValue 对象。

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.

相关非成员

QJSValueList

This is a typedef for a QList < QJSValue >.