QJSManagedValue#
QJSManagedValue
represents a value on the JavaScript heap belonging to a QJSEngine
. More…
Synopsis#
Functions#
def
call
([arguments={}])def
callAsConstructor
([arguments={}])def
callWithInstance
(instance[, arguments={}])def
deleteProperty
(name)def
deleteProperty
(arrayIndex)def
engine
()def
equals
(other)def
hasOwnProperty
(name)def
hasOwnProperty
(arrayIndex)def
hasProperty
(name)def
hasProperty
(arrayIndex)def
isArray
()def
isBoolean
()def
isDate
()def
isError
()def
isFunction
()def
isInteger
()def
isJsMetaType
()def
isNull
()def
isNumber
()def
isObject
()def
isQMetaObject
()def
isQObject
()def
isRegularExpression
()def
isString
()def
isSymbol
()def
isUndefined
()def
isUrl
()def
isVariant
()def
jsMetaInstantiate
([values={}])def
jsMetaMembers
()def
jsMetaType
()def
property
(name)def
property
(arrayIndex)def
prototype
()def
setProperty
(name, value)def
setProperty
(arrayIndex, value)def
setPrototype
(prototype)def
strictlyEquals
(other)def
toBoolean
()def
toDateTime
()def
toInteger
()def
toJSValue
()def
toNumber
()def
toPrimitive
()def
toQMetaObject
()def
toQObject
()def
toRegularExpression
()def
toString
()def
toUrl
()def
toVariant
()def
type
()
Note
This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE
Detailed Description#
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 hasError()
will return true
afterwards. You can then catch the exception using catchError()
, or pass it up the stack, at your own discretion.
Note
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.
- class PySide6.QtQml.QJSManagedValue#
PySide6.QtQml.QJSManagedValue(value, engine)
PySide6.QtQml.QJSManagedValue(value, engine)
PySide6.QtQml.QJSManagedValue(string, engine)
PySide6.QtQml.QJSManagedValue(variant, engine)
- Parameters:
string – str
variant – object
engine –
PySide6.QtQml.QJSEngine
value –
PySide6.QtQml.QJSValue
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
. If 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 string
using the heap of engine
.
Creates a QJSManagedValue
from variant
using the heap of engine
.
- PySide6.QtQml.QJSManagedValue.Type#
This enum represents the JavaScript native types, as specified by ECMA-262 .
Constant
Description
QJSManagedValue.Undefined
The
undefined
typeQJSManagedValue.Boolean
The
boolean
typeQJSManagedValue.Number
The
number
typeQJSManagedValue.String
The
string
typeQJSManagedValue.Object
The
object
typeQJSManagedValue.Symbol
The
symbol
typeQJSManagedValue.Function
The
function
type
Note that the 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()
method.
- PySide6.QtQml.QJSManagedValue.call([arguments={}])#
- Parameters:
arguments – .list of QJSValue
- Return type:
If this QJSManagedValue
represents a JavaScript FunctionObject, calls it with the given arguments
, and returns the result. Otherwise returns a JavaScript undefined
value.
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.
- PySide6.QtQml.QJSManagedValue.callAsConstructor([arguments={}])#
- Parameters:
arguments – .list of QJSValue
- Return type:
If this QJSManagedValue
represents a JavaScript FunctionObject, calls it as constructor with the given arguments
, and returns the result. Otherwise returns a JavaScript undefined
value.
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.
- PySide6.QtQml.QJSManagedValue.callWithInstance(instance[, arguments={}])#
- Parameters:
instance –
PySide6.QtQml.QJSValue
arguments – .list of QJSValue
- Return type:
If this QJSManagedValue
represents a JavaScript FunctionObject, calls it on instance
with the given arguments
, and returns the result. Otherwise returns a JavaScript undefined
value.
The arguments
and the 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.
- PySide6.QtQml.QJSManagedValue.deleteProperty(name)#
- Parameters:
name – str
- Return type:
bool
Deletes the property name
from this QJSManagedValue
. Returns true
if the deletion succeeded, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.deleteProperty(arrayIndex)
- Parameters:
arrayIndex – int
- Return type:
bool
Deletes the value stored at arrayIndex
from this QJSManagedValue
. Returns true
if the deletion succeeded, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.engine()#
- Return type:
Returns the 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.
- PySide6.QtQml.QJSManagedValue.equals(other)#
- Parameters:
other –
PySide6.QtQml.QJSManagedValue
- Return type:
bool
Invokes the JavaScript ‘==’ operator on this QJSManagedValue
and other
, and returns the result.
See also
- PySide6.QtQml.QJSManagedValue.hasOwnProperty(name)#
- Parameters:
name – str
- Return type:
bool
Returns true
if this QJSManagedValue
has a property name
, otherwise returns false
. The properties of the prototype chain are not considered.
- PySide6.QtQml.QJSManagedValue.hasOwnProperty(arrayIndex)
- Parameters:
arrayIndex – int
- Return type:
bool
Returns true
if this QJSManagedValue
has an array index arrayIndex
, otherwise returns false
. The properties of the prototype chain are not considered.
- PySide6.QtQml.QJSManagedValue.hasProperty(name)#
- Parameters:
name – str
- Return type:
bool
Returns true
if this QJSManagedValue
has a property name
, otherwise returns false
. The properties of the prototype chain are considered.
- PySide6.QtQml.QJSManagedValue.hasProperty(arrayIndex)
- Parameters:
arrayIndex – int
- Return type:
bool
Returns true
if this QJSManagedValue
has an array index arrayIndex
, otherwise returns false
. The properties of the prototype chain are considered.
- PySide6.QtQml.QJSManagedValue.isArray()#
- Return type:
bool
Returns true
if this value represents a JavaScript Array object, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isBoolean()#
- Return type:
bool
Returns true
if the type of this QJSManagedValue
is boolean
, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isDate()#
- Return type:
bool
Returns true
if this value represents a JavaScript Date object, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isError()#
- Return type:
bool
Returns true
if this value represents a JavaScript Error object, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isFunction()#
- Return type:
bool
Returns true
if the type of this QJSManagedValue
is function
, false
otherwise.
- PySide6.QtQml.QJSManagedValue.isInteger()#
- Return type:
bool
Returns true
if this 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.
- PySide6.QtQml.QJSManagedValue.isJsMetaType()#
- Return type:
bool
- PySide6.QtQml.QJSManagedValue.isNull()#
- Return type:
bool
Returns true
if this QJSManagedValue
holds the JavaScript null
value, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isNumber()#
- Return type:
bool
Returns true
if the type of this QJSManagedValue
is number
, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isObject()#
- Return type:
bool
Returns true
if the type of this QJSManagedValue
is object
, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isQMetaObject()#
- Return type:
bool
Returns true
if this value represents a QMetaObject pointer managed on the JavaScript heap, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isQObject()#
- Return type:
bool
Returns true
if this value represents a QObject pointer managed on the JavaScript heap, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isRegularExpression()#
- Return type:
bool
Returns true
if this value represents a JavaScript regular expression object, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isString()#
- Return type:
bool
Returns true
if the type of this QJSManagedValue
is string
, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isSymbol()#
- Return type:
bool
Returns true
if the type of this QJSManagedValue
is symbol
, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isUndefined()#
- Return type:
bool
Returns true
if the type of this QJSManagedValue
is undefined
, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isUrl()#
- Return type:
bool
Returns true
if this value represents a JavaScript Url object, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.isVariant()#
- Return type:
bool
Returns true
if this value represents a QVariant managed on the JavaScript heap, or false
otherwise.
- PySide6.QtQml.QJSManagedValue.jsMetaInstantiate([values={}])#
- Parameters:
values – .list of QJSValue
- Return type:
- PySide6.QtQml.QJSManagedValue.jsMetaMembers()#
- Return type:
list of strings
- PySide6.QtQml.QJSManagedValue.jsMetaType()#
- Return type:
- PySide6.QtQml.QJSManagedValue.property(name)#
- Parameters:
name – str
- Return type:
Returns the property name
of this QJSManagedValue
. The prototype chain is searched if the property is not found on the actual object.
See also
- PySide6.QtQml.QJSManagedValue.property(arrayIndex)
- Parameters:
arrayIndex – int
- Return type:
Returns the property stored at arrayIndex
of this QJSManagedValue
. The prototype chain is searched if the property is not found on the actual object.
- PySide6.QtQml.QJSManagedValue.prototype()#
- Return type:
Returns the prototype for this QJSManagedValue
. This works on any value. You can, for example retrieve the JavaScript boolean
prototype from a boolean
value.
See also
- PySide6.QtQml.QJSManagedValue.setProperty(name, value)#
- Parameters:
name – str
value –
PySide6.QtQml.QJSValue
Sets the property name
to value
on this QJSManagedValue
. This can only be done on JavaScript values of type object
. Furhermore, value
has to be either a primitive or belong to the same engine as this value.
See also
- PySide6.QtQml.QJSManagedValue.setProperty(arrayIndex, value)
- Parameters:
arrayIndex – int
value –
PySide6.QtQml.QJSValue
Stores the value
at arrayIndex
in this QJSManagedValue
. This can only be done on JavaScript values of type object
, 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.
- PySide6.QtQml.QJSManagedValue.setPrototype(prototype)#
- Parameters:
prototype –
PySide6.QtQml.QJSManagedValue
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.
See also
- PySide6.QtQml.QJSManagedValue.strictlyEquals(other)#
- Parameters:
other –
PySide6.QtQml.QJSManagedValue
- Return type:
bool
Invokes the JavaScript ‘===’ operator on this QJSManagedValue
and other
, and returns the result.
See also
- PySide6.QtQml.QJSManagedValue.toBoolean()#
- Return type:
bool
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.
- PySide6.QtQml.QJSManagedValue.toDateTime()#
- Return type:
If this QJSManagedValue
holds a JavaScript Date object, returns an equivalent QDateTime. Otherwise returns an invalid one.
- PySide6.QtQml.QJSManagedValue.toInteger()#
- Return type:
int
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.
Note
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.
Note
The JavaScript rules for coercing numbers into 32bit integers are unintuitive.
- PySide6.QtQml.QJSManagedValue.toJSValue()#
- Return type:
Copies this QJSManagedValue
into a new QJSValue
. This is less efficient than move-constructing a QJSValue
from a QJSManagedValue
, but retains the QJSManagedValue
.
- PySide6.QtQml.QJSManagedValue.toNumber()#
- Return type:
float
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.
Note
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.
- PySide6.QtQml.QJSManagedValue.toPrimitive()#
- Return type:
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
.
Note
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.
- PySide6.QtQml.QJSManagedValue.toQMetaObject()#
- Return type:
If this QJSManagedValue
holds a QMetaObject pointer, returns it. Otherwise returns nullptr.
- PySide6.QtQml.QJSManagedValue.toQObject()#
- Return type:
If this QJSManagedValue
holds a QObject pointer, returns it. Otherwise returns nullptr.
- PySide6.QtQml.QJSManagedValue.toRegularExpression()#
- Return type:
If this QJSManagedValue
holds a JavaScript regular expression object, returns an equivalent QRegularExpression. Otherwise returns an invalid one.
- PySide6.QtQml.QJSManagedValue.toString()#
- Return type:
str
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.
Note
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.
- PySide6.QtQml.QJSManagedValue.toUrl()#
- Return type:
If this QJSManagedValue
holds a JavaScript Url object, returns an equivalent QUrl. Otherwise returns an invalid one.
- PySide6.QtQml.QJSManagedValue.toVariant()#
- Return type:
object
Copies this QJSManagedValue
into a new QVariant. This also creates a useful QVariant if isVariant()
returns false. QVariant can hold all types supported by QJSManagedValue
.
Returns the JavaScript type of this QJSManagedValue
.