QScriptValue Class Reference
[QtScript module]

Detailed Description

The QScriptValue class acts as a container for the Qt Script data types.

QScriptValue supports the types defined in the ECMA-262 standard: The primitive types, which are Undefined, Null, Boolean, Number, and String; and the Object type. Additionally, Qt Script has built-in support for QVariant, QObject and QMetaObject.

For the object-based types (including Date and RegExp), use the newT() functions in QScriptEngine (e.g. QScriptEngine::newObject()) to create a QScriptValue of the desired type. For the primitive types, use one of the QScriptValue constructor overloads.

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 QScriptValue to another type. You can also use the generic qscriptvalue_cast() function.

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

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

Each property can have a set of attributes; these are specified as the third (optional) argument to setProperty(). The attributes of a property can be queried by calling the propertyFlags() function. The following code snippet creates a property that cannot be modified by script code:

 QScriptValue val(&myEngine, 123);
 myObject.setProperty("myReadOnlyProperty", val, QScriptValue::ReadOnly);

If you want to iterate over the properties of a script object, use the QScriptValueIterator class.

Object values have an internal prototype property, which can be accessed with prototype() and setPrototype(). Properties added to a prototype are shared by all objects having that prototype; this is referred to as prototype-based inheritance. In practice, it means that (by default) the property() function will automatically attempt to look up look the property in the prototype() (and in the prototype of the prototype(), and so on), if the object itself does not have the requested property. Note that this prototype-based lookup is not performed by setProperty(); setProperty() will always create the property in the script object itself. For more information, see the QtScript documentation.

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

Use equals(), strictlyEquals() and lessThan() to compare a QScriptValue to another.

Object values can have custom data associated with them; see the setData() and data() functions. By default, this data is not accessible to scripts; it can be used to store any data you want to associate with the script object. Typically this is used by custom class objects (see QScriptClass) to store a C++ type that contains the "native" object data.

Note that a QScriptValue for which isObject() is true only carries a reference to an actual object; copying the QScriptValue 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 QScriptValueIterator in C++.

See also QScriptEngine and QScriptValueIterator.

Member Type Documentation

enum QScriptValue::PropertyFlag
flags QScriptValue::PropertyFlags

This enum describes the attributes of a property.

The PropertyFlags type is a typedef for QFlags<PropertyFlag>. It stores an OR combination of PropertyFlag values.

enum QScriptValue::ResolveFlag
flags QScriptValue::ResolveFlags

This enum specifies how to look up a property of an object.

The ResolveFlags type is a typedef for QFlags<ResolveFlag>. It stores an OR combination of ResolveFlag values.

enum QScriptValue::SpecialValue

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

Member Function Documentation

QScriptValue::QScriptValue ()

Constructs an invalid QScriptValue.

QScriptValue::QScriptValue ( const QScriptValue & other )

Constructs a new QScriptValue that is a copy of other.

Note that if 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).

QScriptValue::QScriptValue ( SpecialValue value )

Constructs a new QScriptValue with a special value.

This function was introduced in Qt 4.5.

QScriptValue::QScriptValue ( bool value )

Constructs a new QScriptValue with a boolean value.

This function was introduced in Qt 4.5.

QScriptValue::QScriptValue ( int value )

Constructs a new QScriptValue with a number value.

This function was introduced in Qt 4.5.

QScriptValue::QScriptValue ( uint value )

Constructs a new QScriptValue with a number value.

This function was introduced in Qt 4.5.

QScriptValue::QScriptValue ( qsreal value )

Constructs a new QScriptValue with a number value.

This function was introduced in Qt 4.5.

QScriptValue::QScriptValue ( const QString & value )

Constructs a new QScriptValue with a string value.

This function was introduced in Qt 4.5.

QScriptValue::QScriptValue ( const QLatin1String & value )

Constructs a new QScriptValue with a string value.

This function was introduced in Qt 4.5.

QScriptValue::QScriptValue ( const char * value )

Constructs a new QScriptValue with a string value.

This function was introduced in Qt 4.5.

QScriptValue::~QScriptValue ()

Destroys this QScriptValue.

QScriptValue QScriptValue::call ( const QScriptValue & thisObject = QScriptValue(), const QScriptValueList & args = QScriptValueList() )

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

If this QScriptValue is not a function, call() does nothing and returns an invalid QScriptValue.

Note that if thisObject is not an object, the global object (see QScriptEngine::globalObject()) will be used as the `this' object.

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 QScriptEngine::hasUncaughtException() to determine if an exception occurred.

 QScriptEngine engine;
 engine.evaluate("function fullName() { return this.firstName + ' ' + this.lastName; }");
 engine.evaluate("somePerson = { firstName: 'John', lastName: 'Doe' }");

 QScriptValue global = engine.globalObject();
 QScriptValue fullName = global.property("fullName");
 QScriptValue who = global.property("somePerson");
 qDebug() << fullName.call(who).toString(); // "John Doe"

 engine.evaluate("function cube(x) { return x * x * x; }");
 QScriptValue cube = global.property("cube");
 QScriptValueList args;
 args << 3;
 qDebug() << cube.call(QScriptValue(), args).toNumber(); // 27

See also construct().

QScriptValue QScriptValue::call ( const QScriptValue & thisObject, const QScriptValue & arguments )

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

If this QScriptValue is not a function, call() does nothing and returns an invalid QScriptValue.

arguments can be an arguments object, an array, null or undefined; any other type will cause a TypeError to be thrown.

Note that if thisObject is not an object, the global object (see QScriptEngine::globalObject()) will be used as the `this' object.

One common usage of this function is to forward native function calls to another function:

 QScriptValue myNativeFunction(QScriptContext *ctx, QScriptEngine *)
 {
     QScriptValue otherFunction = ...;
     return otherFunction.call(ctx->thisObject(), ctx->argumentsObject());
 }

See also construct() and QScriptContext::argumentsObject().

QScriptValue QScriptValue::construct ( const QScriptValueList & args = QScriptValueList() )

Creates a new Object and calls this QScriptValue 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.

If this QScriptValue is not a function, construct() does nothing and returns an invalid QScriptValue.

Calling construct() can cause an exception to occur in the script engine; in that case, construct() returns the value that was thrown (typically an Error object). You can call QScriptEngine::hasUncaughtException() to determine if an exception occurred.

See also call() and QScriptEngine::newObject().

QScriptValue QScriptValue::construct ( const QScriptValue & arguments )

Creates a new Object and calls this QScriptValue as a constructor, using the created object as the `this' object and passing arguments 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.

If this QScriptValue is not a function, construct() does nothing and returns an invalid QScriptValue.

arguments can be an arguments object, an array, null or undefined. Any other type will cause a TypeError to be thrown.

See also call(), QScriptEngine::newObject(), and QScriptContext::argumentsObject().

QScriptValue QScriptValue::data () const

Returns the internal data of this QScriptValue object. QtScript uses this property to store the primitive value of Date, String, Number and Boolean objects. For other types of object, custom data may be stored using setData().

This function was introduced in Qt 4.4.

See also setData().

QScriptEngine * QScriptValue::engine () const

Returns the QScriptEngine that created this QScriptValue, or 0 if this QScriptValue is invalid or the value is not associated with a particular engine.

bool QScriptValue::equals ( const QScriptValue & other ) const

Returns true if this QScriptValue is equal to 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 QScriptValue 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 String 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 QScriptValue or the 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).

See also strictlyEquals() and lessThan().

bool QScriptValue::instanceOf ( const QScriptValue & other ) const

Returns true if this QScriptValue is an instance of other; otherwise returns false.

This QScriptValue is considered to be an instance of other if other is a function and the value of the prototype property of other is in the prototype chain of this QScriptValue.

bool QScriptValue::isArray () const

Returns true if this QScriptValue is an object of the Array class; otherwise returns false.

See also QScriptEngine::newArray().

bool QScriptValue::isBool () const

Returns true if this QScriptValue is of the primitive type Boolean; otherwise returns false.

This function was introduced in Qt 4.5.

See also toBool().

bool QScriptValue::isDate () const

Returns true if this QScriptValue is an object of the Date class; otherwise returns false.

See also QScriptEngine::newDate().

bool QScriptValue::isError () const

Returns true if this QScriptValue is an object of the Error class; otherwise returns false.

See also QScriptContext::throwError().

bool QScriptValue::isFunction () const

Returns true if this QScriptValue is a function; otherwise returns false.

See also call().

bool QScriptValue::isNull () const

Returns true if this QScriptValue is of the primitive type Null; otherwise returns false.

See also QScriptEngine::nullValue().

bool QScriptValue::isNumber () const

Returns true if this QScriptValue is of the primitive type Number; otherwise returns false.

See also toNumber().

bool QScriptValue::isObject () const

Returns true if this QScriptValue 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.

See also toObject() and QScriptEngine::newObject().

bool QScriptValue::isQMetaObject () const

Returns true if this QScriptValue is a QMetaObject; otherwise returns false.

See also toQMetaObject() and QScriptEngine::newQMetaObject().

bool QScriptValue::isQObject () const

Returns true if this QScriptValue is a QObject; otherwise returns false.

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

See also toQObject() and QScriptEngine::newQObject().

bool QScriptValue::isRegExp () const

Returns true if this QScriptValue is an object of the RegExp class; otherwise returns false.

See also QScriptEngine::newRegExp().

bool QScriptValue::isString () const

Returns true if this QScriptValue is of the primitive type String; otherwise returns false.

See also toString().

bool QScriptValue::isUndefined () const

Returns true if this QScriptValue is of the primitive type Undefined; otherwise returns false.

See also QScriptEngine::undefinedValue().

bool QScriptValue::isValid () const

Returns true if this QScriptValue is valid; otherwise returns false.

bool QScriptValue::isVariant () const

Returns true if this QScriptValue is a variant value; otherwise returns false.

See also toVariant() and QScriptEngine::newVariant().

bool QScriptValue::lessThan ( const QScriptValue & other ) const

Returns true if this QScriptValue is less than other, otherwise returns false. The comparison follows the behavior described in ECMA-262 section 11.8.5, "The Abstract Relational Comparison Algorithm".

Note that if this QScriptValue or the 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).

See also equals().

QScriptValue QScriptValue::property ( const QString & name, const ResolveFlags & mode = ResolvePrototype ) const

Returns the value of this QScriptValue's property with the given name, using the given mode to resolve the property.

If no such property exists, an invalid QScriptValue is returned.

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 object).

See also setProperty(), propertyFlags(), and QScriptValueIterator.

QScriptValue QScriptValue::property ( const QScriptString & name, const ResolveFlags & mode = ResolvePrototype ) const

Returns the value of this QScriptValue's property with the given name, using the given mode to resolve the property.

This overload of property() is useful when you need to look up the same property repeatedly, since the lookup can be performed faster when the name is represented as an interned string.

This function was introduced in Qt 4.4.

See also QScriptEngine::toStringHandle() and setProperty().

QScriptValue QScriptValue::property ( quint32 arrayIndex, const ResolveFlags & mode = ResolvePrototype ) const

This is an overloaded function.

Returns the property at the given arrayIndex, using the given mode to resolve the property.

This function is provided for convenience and performance when working with array objects.

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

QScriptValue::PropertyFlags QScriptValue::propertyFlags ( const QString & name, const ResolveFlags & mode = ResolvePrototype ) const

Returns the flags of the property with the given name, using the given mode to resolve the property.

See also property().

QScriptValue::PropertyFlags QScriptValue::propertyFlags ( const QScriptString & name, const ResolveFlags & mode = ResolvePrototype ) const

Returns the flags of the property with the given name, using the given mode to resolve the property.

This function was introduced in Qt 4.4.

See also property().

QScriptValue QScriptValue::prototype () const

If this QScriptValue is an object, returns the internal prototype (__proto__ property) of this object; otherwise returns an invalid QScriptValue.

See also setPrototype() and isObject().

QScriptValue QScriptValue::scope () const

Returns the scope object of this QScriptValue. This function is only relevant for function objects. The scope determines how variables are resolved when the function is invoked.

See also setScope().

QScriptClass * QScriptValue::scriptClass () const

Returns the custom script class that this script object is an instance of, or 0 if the object is not of a custom class.

This function was introduced in Qt 4.4.

See also setScriptClass().

void QScriptValue::setData ( const QScriptValue & data )

Sets the internal data of this QScriptValue object. You can use this function to set object-specific data that won't be directly accessible to scripts, but may be retrieved in C++ using the data() function.

This function was introduced in Qt 4.4.

See also data().

void QScriptValue::setProperty ( const QString & name, const QScriptValue & value, const PropertyFlags & flags = KeepExistingFlags )

Sets the value of this QScriptValue's property with the given name to the given value.

If this QScriptValue is not an object, this function does nothing.

If this QScriptValue does not already have a property with name name, a new property is created; the given flags then specify how this property may be accessed by script code.

If value is invalid, the property is removed.

If the property is implemented using a setter function (i.e. has the PropertySetter flag set), calling setProperty() has side-effects on the script engine, since the setter function will be called with the given value as argument (possibly resulting in an uncaught script exception).

Note that you cannot specify custom getter or setter functions for built-in properties, such as the length property of Array objects or meta properties of QObject objects.

See also property().

void QScriptValue::setProperty ( const QScriptString & name, const QScriptValue & value, const PropertyFlags & flags = KeepExistingFlags )

Sets the value of this QScriptValue's property with the given name to the given value. The given flags specify how this property may be accessed by script code.

This overload of setProperty() is useful when you need to set the same property repeatedly, since the operation can be performed faster when the name is represented as an interned string.

This function was introduced in Qt 4.4.

See also QScriptEngine::toStringHandle().

void QScriptValue::setProperty ( quint32 arrayIndex, const QScriptValue & value, const PropertyFlags & flags = KeepExistingFlags )

This is an overloaded function.

Sets the property at the given arrayIndex to the given value.

This function is provided for convenience and performance when working with array objects.

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

void QScriptValue::setPrototype ( const QScriptValue & prototype )

If this QScriptValue is an object, sets the internal prototype (__proto__ property) of this object to be prototype; 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.

See also prototype() and isObject().

void QScriptValue::setScope ( const QScriptValue & scope )

Sets the scope object of this QScriptValue. This function is only relevant for function objects. Changing the scope is useful when creating closures; see Nested Functions and the Scope Chain.

See also scope().

void QScriptValue::setScriptClass ( QScriptClass * scriptClass )

Sets the custom script class of this script object to scriptClass. This can be used to "promote" a plain script object (e.g. created by the "new" operator in a script, or by QScriptEngine::newObject() in C++) to an object of a custom type.

If scriptClass is 0, the object will be demoted to a plain script object.

This function was introduced in Qt 4.4.

See also scriptClass() and setData().

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

Returns true if this QScriptValue is equal to 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 QScriptValue 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:

See also equals().

bool QScriptValue::toBool () const

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

Note that if this QScriptValue 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).

This function was introduced in Qt 4.5.

See also isBool().

QDateTime QScriptValue::toDateTime () const

Returns a QDateTime representation of this value, in local time. If this QScriptValue is not a date, or the value of the date is NaN (Not-a-Number), an invalid QDateTime is returned.

See also isDate().

qint32 QScriptValue::toInt32 () const

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

Note that if this QScriptValue 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).

See also toNumber() and toUInt32().

qsreal QScriptValue::toInteger () const

Returns the integer value of this QScriptValue, using the conversion rules described in ECMA-262 section 9.4, "ToInteger".

Note that if this QScriptValue 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).

See also toNumber().

qsreal QScriptValue::toNumber () const

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

Note that if this QScriptValue 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).

See also isNumber(), toInteger(), toInt32(), toUInt32(), and toUInt16().

const QMetaObject * QScriptValue::toQMetaObject () const

If this QScriptValue is a QMetaObject, returns the QMetaObject pointer that the QScriptValue represents; otherwise, returns 0.

See also isQMetaObject().

QObject * QScriptValue::toQObject () const

If this QScriptValue is a QObject, returns the QObject pointer that the QScriptValue represents; otherwise, returns 0.

If the QObject that this QScriptValue wraps has been deleted, this function returns 0 (i.e. it is possible for toQObject() to return 0 even when isQObject() returns true).

See also isQObject().

QRegExp QScriptValue::toRegExp () const

Returns the QRegExp representation of this value. If this QScriptValue is not a regular expression, an empty QRegExp is returned.

See also isRegExp().

QString QScriptValue::toString () const

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

Note that if this QScriptValue 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).

See also isString().

quint16 QScriptValue::toUInt16 () const

Returns the unsigned 16-bit integer value of this QScriptValue, using the conversion rules described in ECMA-262 section 9.7, "ToUint16".

Note that if this QScriptValue 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).

See also toNumber().

quint32 QScriptValue::toUInt32 () const

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

Note that if this QScriptValue 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).

See also toNumber() and toInt32().

QVariant QScriptValue::toVariant () const

Returns the QVariant value of this QScriptValue, if it can be converted to a QVariant; otherwise returns an invalid QVariant. The conversion is performed according to the following table:

See also isVariant().

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

Assigns the other value to this QScriptValue.

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

Related Non-Members

T qscriptvalue_cast ( const QScriptValue & value )

Returns the given value converted to the template type T.

This function was introduced in Qt 4.3.

See also qScriptRegisterMetaType() and QScriptEngine::toScriptValue().