QJSManagedValue represents a value on the JavaScript heap belonging to a QJSEngine . 更多...
| 头： | #include <QJSManagedValue> |
| CMake: |
find_package(Qt6 REQUIRED COMPONENTS Qml)
target_link_libraries(mytarget PRIVATE Qt6::Qml) |
| qmake: | QT += qml |
| Since: | Qt 6.1 |
| enum | Type { Undefined, Boolean, Number, String, Object, …, Function } |
| QJSManagedValue () | |
| QJSManagedValue (QJSValue value , QJSEngine * engine ) | |
| QJSManagedValue (const QJSPrimitiveValue & value , QJSEngine * engine ) | |
| QJSManagedValue (const QVariant & variant , QJSEngine * engine ) | |
| QJSManagedValue (const QString & string , QJSEngine * engine ) | |
| QJSManagedValue (QJSManagedValue && other ) | |
| ~QJSManagedValue () | |
| QJSValue | call (const QJSValueList & arguments = {}) const |
| QJSValue | callAsConstructor (const QJSValueList & arguments = {}) const |
| QJSValue | callWithInstance (const QJSValue & instance , const QJSValueList & arguments = {}) const |
| bool | deleteProperty (const QString & name ) |
| bool | deleteProperty (quint32 arrayIndex ) |
| QJSEngine * | engine () const |
| bool | 等于 (const QJSManagedValue & other ) const |
| bool | hasOwnProperty (const QString & name ) const |
| bool | hasOwnProperty (quint32 arrayIndex ) const |
| bool | hasProperty (const QString & name ) const |
| bool | hasProperty (quint32 arrayIndex ) const |
| bool | isArray () const |
| bool | isBoolean () const |
| bool | isDate () const |
| bool | isError () const |
| bool | isFunction () const |
| bool | isInteger () const |
| bool | isNull () const |
| bool | isNumber () const |
| bool | isObject () const |
| bool | isQMetaObject () const |
| bool | isQObject () const |
| bool | isRegularExpression () const |
| bool | isString () const |
| bool | isSymbol () const |
| bool | isUndefined () const |
| bool | isUrl () const |
| bool | isVariant () const |
| QJSValue | property (const QString & name ) const |
| QJSValue | property (quint32 arrayIndex ) const |
| QJSManagedValue | prototype () const |
| void | setProperty (const QString & name , const QJSValue & value ) |
| void | setProperty (quint32 arrayIndex , const QJSValue & value ) |
| void | setPrototype (const QJSManagedValue & prototype ) |
| bool | strictlyEquals (const QJSManagedValue & other ) const |
| bool | toBoolean () const |
| QDateTime | toDateTime () const |
| int | toInteger () const |
| QJSValue | toJSValue () const |
| double | toNumber () const |
| QJSPrimitiveValue | toPrimitive () const |
| const QMetaObject * | toQMetaObject () const |
| QObject * | toQObject () const |
| QRegularExpression | toRegularExpression () const |
| QString | toString () const |
| QUrl | toUrl () const |
| QVariant | toVariant () const |
| QJSManagedValue::Type | type () const |
| QJSManagedValue & | operator= (QJSManagedValue && other ) |
The QJSManagedValue class allows interaction with JavaScript values in most ways you can interact with them from JavaScript itself. You can get and set properties and prototypes, and you can access arrays. Additionally, you can transform the value into the Qt counterparts of JavaScript objects. For example, a Url object may be transformed into a QUrl .
A QJSManagedValue is always bound to a particular QJSEngine . You cannot use it independently. This means that you cannot have a QJSManagedValue from one engine be a property or a proptotype of a QJSManagedValue from a different engine.
In contrast to
QJSValue
, almost all values held by QJSManagedValue live on the JavaScript heap. There is no inline or unmanaged storage. Therefore, you can get the prototype of a primitive value, and you can get the
length
property of a string.
Only default-constructed or moved-from QJSManagedValues do not hold a value on the JavaScript heap. They represent
undefined
, which doesn't have any properties or prototypes.
Also in contrast to
QJSValue
, QJSManagedValue does not catch any JavaScript exceptions. If an operation on a QJSManagedValue causes an error, it will generally return an
undefined
value and
QJSEngine::hasError
() 会返回
true
afterwards. You can then catch the exception using
QJSEngine::catchError
(), or pass it up the stack, at your own discretion.
注意： As the reference to the value on the JavaScript heap has to be freed on destruction, you cannot move a QJSManagedValue to a different thread. The destruction would take place in the new thread, which would create a race condition with the garbage collector on the original thread. This also means that you cannot hold a QJSManagedValue beyond the lifespan of its engine.
The recommended way of working with a QJSManagedValue is creating it on the stack, possibly by moving a QJSValue and adding an engine, then performing the necessary operations on it, and finally moving it back into a QJSValue for storage. Moving between QJSManagedValue and QJSValue is fast.
This enum represents the JavaScript native types, as specified by ECMA-262 .
| 常量 | 值 | 描述 |
|---|---|---|
QJSManagedValue::Undefined
|
0
|
The
undefined
type
|
QJSManagedValue::Boolean
|
1
|
The
boolean
type
|
QJSManagedValue::Number
|
2
|
The
编号
type
|
QJSManagedValue::String
|
3
|
The
string
type
|
QJSManagedValue::Object
|
4
|
The
对象
type
|
QJSManagedValue::Symbol
|
5
|
The
symbol
type
|
QJSManagedValue::Function
|
6
|
The
function
type
|
注意，
null
value is not a type of itself but rather a special kind of object. You can query a
QJSManagedValue
for this condition using the
isNull
() method. Furthermore, JavaScript has no integer type, but it knows a special treatment of numbers in preparation for integer only operations. You can query a
QJSManagedValue
to find out whether it holds the result of such a treatment by using the
isInteger
() 方法。
Creates a QJSManagedValue that represents the JavaScript
undefined
value. This is the only value not stored on the JavaScript heap. Calling
engine
() on a default-constructed QJSManagedValue will return nullptr.
Creates a QJSManagedValue from
value
, using the heap of
engine
。若
value
is itself managed and the engine it belongs to is not
engine
, the result is an
undefined
value, and a warning is generated.
Creates a QJSManagedValue from value using the heap of engine .
Creates a QJSManagedValue from variant using the heap of engine .
Creates a QJSManagedValue from string using the heap of engine .
Move-constructs a QJSManagedValue from other . This leaves other in the default-constructed state where it represents undefined and does not belong to any engine.
销毁 QJSManagedValue .
注意： This frees the memory slot it holds on the JavaScript heap. You must not destroy a QJSManagedValue from a different thread than the one where the QJSEngine it belongs to lives.
若此
QJSManagedValue
represents a JavaScript FunctionObject, calls it with the given
arguments
, and returns the result. Otherwise returns a JavaScript
undefined
值。
The
arguments
have to be either primitive values or belong to the same
QJSEngine
as this
QJSManagedValue
. Otherwise the call is not carried out and a JavaScript
undefined
value is returned.
若此
QJSManagedValue
represents a JavaScript FunctionObject, calls it as constructor with the given
arguments
, and returns the result. Otherwise returns a JavaScript
undefined
值。
The
arguments
have to be either primitive values or belong to the same
QJSEngine
as this
QJSManagedValue
. Otherwise the call is not carried out and a JavaScript
undefined
value is returned.
若此
QJSManagedValue
represents a JavaScript FunctionObject, calls it on
instance
采用给定
arguments
, and returns the result. Otherwise returns a JavaScript
undefined
值。
The
arguments
和
instance
have to be either primitive values or belong to the same
QJSEngine
as this
QJSManagedValue
. Otherwise the call is not carried out and a JavaScript
undefined
value is returned.
Deletes the property
name
从此
QJSManagedValue
。返回
true
if the deletion succeeded, or
false
否则。
Deletes the value stored at
arrayIndex
从此
QJSManagedValue
。返回
true
if the deletion succeeded, or
false
否则。
返回 QJSEngine this QJSManagedValue belongs to. Mind that the engine is always valid, unless the QJSManagedValue is default-constructed or moved from. In the latter case a nullptr is returned.
Invokes the JavaScript '==' operator on this QJSManagedValue and other , and returns the result.
另请参阅 strictlyEquals .
返回
true
若此
QJSManagedValue
has a property
name
，否则返回
false
. The properties of the prototype chain are not considered.
返回
true
若此
QJSManagedValue
has an array index
arrayIndex
，否则返回
false
. The properties of the prototype chain are not considered.
返回
true
若此
QJSManagedValue
has a property
name
，否则返回
false
. The properties of the prototype chain are considered.
返回
true
若此
QJSManagedValue
has an array index
arrayIndex
，否则返回
false
. The properties of the prototype chain are considered.
返回
true
if this value represents a JavaScript Array object, or
false
否则。
返回
true
if the type of this
QJSManagedValue
is
boolean
，或
false
否则。
返回
true
if this value represents a JavaScript Date object, or
false
否则。
返回
true
if this value represents a JavaScript Error object, or
false
否则。
返回
true
if the type of this
QJSManagedValue
is
function
,
false
否则。
返回
true
若此
QJSManagedValue
holds an integer value, or
false
otherwise. The storage format of a number does not affect the result of any operations performed on it, but if an integer is stored, many operations are faster.
返回
true
若此
QJSManagedValue
holds the JavaScript
null
value, or
false
否则。
返回
true
if the type of this
QJSManagedValue
is
编号
，或
false
否则。
返回
true
if the type of this
QJSManagedValue
is
对象
，或
false
否则。
返回
true
if this value represents a
QMetaObject
pointer managed on the JavaScript heap, or
false
否则。
返回
true
if this value represents a
QObject
pointer managed on the JavaScript heap, or
false
否则。
返回
true
if this value represents a JavaScript regular expression object, or
false
否则。
返回
true
if the type of this
QJSManagedValue
is
string
，或
false
否则。
返回
true
if the type of this
QJSManagedValue
is
symbol
，或
false
否则。
返回
true
if the type of this
QJSManagedValue
is
undefined
，或
false
否则。
返回
true
if this value represents a JavaScript Url object, or
false
否则。
返回
true
if this value represents a
QVariant
managed on the JavaScript heap, or
false
否则。
Returns the property name of this QJSManagedValue . The prototype chain is searched if the property is not found on the actual object.
另请参阅 setProperty ().
Returns the property stored at arrayIndex of this QJSManagedValue . The prototype chain is searched if the property is not found on the actual object.
Returns the prototype for this
QJSManagedValue
. This works on any value. You can, for example retrieve the JavaScript
boolean
prototype from a
boolean
值。
另请参阅 setPrototype ().
设置特性
name
to
value
on this
QJSManagedValue
. This can only be done on JavaScript values of type
对象
. Furhermore,
value
has to be either a primitive or belong to the same engine as this value.
另请参阅 property ().
Stores the
value
at
arrayIndex
在此
QJSManagedValue
. This can only be done on JavaScript values of type
对象
, and it's not recommended if the value is not an array. Furhermore,
value
has to be either a primitive or belong to the same engine as this value.
Sets the prototype of this QJSManagedValue to prototype . A precondition is that prototype belongs to the same QJSEngine as this QJSManagedValue and is an object (including null). Furthermore, this QJSManagedValue has to be an object (excluding null), too, and you cannot create prototype cycles.
另请参阅 prototype ().
Invokes the JavaScript '===' operator on this QJSManagedValue and other , and returns the result.
另请参阅 等于 .
Converts the manged value to a boolean. If the managed value holds a boolean, that one is returned. Otherwise a boolean coercion by JavaScript rules is performed.
若此 QJSManagedValue holds a JavaScript Date object, returns an equivalent QDateTime . Otherwise returns an invalid one.
Converts the manged value to an integer. This first converts the value to a number by the rules of toNumber (), and then clamps it into the integer range by the rules given for coercing the arguments to JavaScript bit shift operators into 32bit integers.
Internally, the value may already be stored as an integer, in which case a fast path is taken.
注意： Conversion of a managed value to a number can throw an exception. In particular, symbols cannot be coerced into numbers, or a custom valueOf() method may throw. In this case the result is 0 and the engine carries an error after the conversion.
注意： The JavaScript rules for coercing numbers into 32bit integers are unintuitive.
Copies this QJSManagedValue into a new QJSValue . This is less efficient than move-constructing a QJSValue 从 QJSManagedValue , but retains the QJSManagedValue .
Converts the manged value to a number. If the managed value holds a number, that one is returned. Otherwise a number coercion by JavaScript rules is performed.
注意： Conversion of a managed value to a number can throw an exception. In particular, symbols cannot be coerced into numbers, or a custom valueOf() method may throw. In this case the result is 0 and the engine carries an error after the conversion.
Converts the manged value to a QJSPrimitiveValue . If the managed 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.
若此 QJSManagedValue holds a QMetaObject pointer, returns it. Otherwise returns nullptr.
若此 QJSManagedValue holds a QObject pointer, returns it. Otherwise returns nullptr.
若此 QJSManagedValue holds a JavaScript regular expression object, returns an equivalent QRegularExpression . Otherwise returns an invalid one.
Converts the manged value to a string. If the managed value holds a string, that one is returned. Otherwise a string coercion by JavaScript rules is performed.
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 an empty string and the engine carries an error after the conversion.
若此 QJSManagedValue holds a JavaScript Url object, returns an equivalent QUrl . Otherwise returns an invalid one.
Copies this QJSManagedValue into a new QVariant . This also creates a useful QVariant if QJSManagedValue::isVariant () 返回 false。 QVariant can hold all types supported by QJSManagedValue .
Returns the JavaScript type of this QJSManagedValue .
Move-assigns a QJSManagedValue from other . This leaves other in the default-constructed state where it represents undefined and does not belong to any engine.
注意： This frees the memory slot this QJSManagedValue holds on the JavaScript heap. You must not move-assign a QJSManagedValue on a different thread than the one where the QJSEngine it belongs to lives.
