Local< T > Class Template Reference

#include <v8.h>

Public Member Functions
V8_INLINE	Local ()
template<class S >
V8_INLINE	Local (Local< S > that)
V8_INLINE bool	IsEmpty () const
V8_INLINE void	Clear ()
V8_INLINE T *	operator-> () const
V8_INLINE T *	operator* () const
template<class S >
V8_INLINE bool	operator== (const Local< S > &that) const
template<class S >
V8_INLINE bool	operator== (const PersistentBase< S > &that) const
template<class S >
V8_INLINE bool	operator!= (const Local< S > &that) const
template<class S >
V8_INLINE bool	operator!= (const Persistent< S > &that) const
template<class S >
V8_INLINE Local< S >	As () const

Static Public Member Functions
template<class S >
static V8_INLINE Local< T >	Cast (Local< S > that)
static V8_INLINE Local< T >	New (Isolate *isolate, Local< T > that)
static V8_INLINE Local< T >	New (Isolate *isolate, const PersistentBase< T > &that)
static V8_INLINE Local< T >	New (Isolate *isolate, const TracedGlobal< T > &that)

Friends
class	Utils
template<class F >
class	Eternal
template<class F >
class	PersistentBase
template<class F , class M >
class	Persistent
template<class F >
class	Local
template<class F >
class	MaybeLocal
template<class F >
class	FunctionCallbackInfo
template<class F >
class	PropertyCallbackInfo
class	String
class	Object
class	Context
class	Isolate
class	Private
template<class F >
class	internal::CustomArguments
class	HandleScope
class	EscapableHandleScope
template<class F1 , class F2 , class F3 >
class	PersistentValueMapBase
template<class F1 , class F2 >
class	PersistentValueVector
template<class F >
class	ReturnValue
template<class F >
class	TracedGlobal
Local< Primitive >	Undefined (Isolate *isolate)
Local< Primitive >	Null (Isolate *isolate)
Local< Boolean >	True (Isolate *isolate)
Local< Boolean >	False (Isolate *isolate)

Detailed Description

template<class T>
class v8::Local< T >

An object reference managed by the v8 garbage collector.

All objects returned from v8 have to be tracked by the garbage collector so that it knows that the objects are still alive. Also, because the garbage collector may move objects, it is unsafe to point directly to an object. Instead, all objects are stored in handles which are known by the garbage collector and updated whenever an object moves. Handles should always be passed by value (except in cases like out-parameters) and they should never be allocated on the heap.

There are two types of handles: local and persistent handles.

Local handles are light-weight and transient and typically used in local operations. They are managed by HandleScopes. That means that a HandleScope must exist on the stack when they are created and that they are only valid inside of the HandleScope active during their creation. For passing a local handle to an outer HandleScope, an EscapableHandleScope and its Escape() method must be used.

Persistent handles can be used when storing objects across several independent operations and have to be explicitly deallocated when they're no longer used.

It is safe to extract the object stored in the handle by dereferencing the handle (for instance, to extract the Object* from a Local<Object>); the value will still be governed by a handle behind the scenes and the same rules apply to these values as to their handles.

Definition at line 184 of file v8.h.

Constructor & Destructor Documentation

Local() [1/2]

V8_INLINE Local ( )

inline

Definition at line 186 of file v8.h.

Referenced by V8InspectorClient::ensureDefaultContextInGroup(), and Extension::GetNativeFunctionTemplate().

Local() [2/2]

V8_INLINE Local ( Local< S >  that )

inline

This check fails when trying to convert between incompatible handles. For example, converting from a Local<String> to a Local<Number>.

Definition at line 188 of file v8.h.

Member Function Documentation

As()

V8_INLINE Local<S> As ( ) const

inline

Calling this is equivalent to Local<S>::Cast(). In particular, this is only valid if the handle actually refers to a value of the target type.

Definition at line 272 of file v8.h.

References Local< T >::Local.

Cast()

static V8_INLINE Local<T> Cast ( Local< S >  that )

inlinestatic

Cast a handle to a subclass, e.g. Local<Value> to Local<Object>. This is only valid if the handle actually refers to a value of the target type.

Definition at line 257 of file v8.h.

References Local< T >::Local.

Clear()

V8_INLINE void Clear ( )

inline

Sets the handle to be empty. IsEmpty() will then return true.

Definition at line 206 of file v8.h.

IsEmpty()

V8_INLINE bool IsEmpty ( ) const

inline

Returns true if the handle is empty.

Definition at line 201 of file v8.h.

Referenced by ScriptOrigin::ScriptOrigin().

New() [1/3]

Local< T > New ( Isolate *  isolate, const PersistentBase< T > &  that  )

static

Definition at line 9973 of file v8.h.

New() [2/3]

Local< T > New ( Isolate *  isolate, const TracedGlobal< T > &  that  )

static

Definition at line 9978 of file v8.h.

New() [3/3]

Local< T > New ( Isolate *  isolate, Local< T >  that  )

static

Create a local handle for the content of another handle. The referee is kept alive by the local handle even when the original handle is destroyed/disposed.

Definition at line 9968 of file v8.h.

operator!=() [1/2]

V8_INLINE bool operator!= ( const Local< S > &  that ) const

inline

Checks whether two handles are different. Returns true if only one of the handles is empty, or if the objects to which they refer are different. The handles' references are not checked.

Definition at line 243 of file v8.h.

operator!=() [2/2]

V8_INLINE bool operator!= ( const Persistent< S > &  that ) const

inline

Definition at line 247 of file v8.h.

operator*()

V8_INLINE T* operator* ( ) const

inline

Definition at line 210 of file v8.h.

operator->()

V8_INLINE T* operator-> ( ) const

inline

Definition at line 208 of file v8.h.

Referenced by Context::Scope::Scope(), ScriptOrigin::ScriptOrigin(), and Context::Scope::~Scope().

operator==() [1/2]

V8_INLINE bool operator== ( const Local< S > &  that ) const

inline

Checks whether two handles are the same. Returns true if both are empty, or if the objects to which they refer are identical. The handles' references are not checked.

Definition at line 219 of file v8.h.

operator==() [2/2]

V8_INLINE bool operator== ( const PersistentBase< S > &  that ) const

inline

Definition at line 227 of file v8.h.

Friends And Related Function Documentation

Context

friend class Context

friend

Definition at line 298 of file v8.h.

EscapableHandleScope

friend class EscapableHandleScope

friend

Definition at line 307 of file v8.h.

Eternal

friend class Eternal

friend

Definition at line 288 of file v8.h.

False

Local<Boolean> False ( Isolate *  isolate )

friend

Definition at line 11129 of file v8.h.

Referenced by Boolean::New().

FunctionCallbackInfo

friend class FunctionCallbackInfo

friend

Definition at line 294 of file v8.h.

HandleScope

friend class HandleScope

friend

Definition at line 306 of file v8.h.

internal::CustomArguments

friend class internal::CustomArguments

friend

Definition at line 301 of file v8.h.

Isolate

friend class Isolate

friend

Definition at line 299 of file v8.h.

Local

friend class Local

friend

Definition at line 291 of file v8.h.

Referenced by Local< T >::As(), Local< T >::Cast(), FunctionCallbackInfo< T >::Data(), PropertyCallbackInfo< T >::Data(), String::Empty(), V8InspectorClient::ensureDefaultContextInGroup(), EscapableHandleScope::Escape(), EscapableHandleScope::EscapeMaybe(), MaybeLocal< T >::FromMaybe(), ReturnValue< T >::Get(), PersistentValueMapBase< K, V, Traits >::Get(), Eternal< T >::Get(), PersistentBase< T >::Get(), TracedGlobal< T >::Get(), PersistentValueVector< V, Traits >::Get(), Isolate::GetDataFromSnapshotOnce(), Context::GetDataFromSnapshotOnce(), Context::GetEmbedderData(), Object::GetInternalField(), Extension::GetNativeFunctionTemplate(), FunctionCallbackInfo< T >::Holder(), PropertyCallbackInfo< T >::Holder(), PersistentValueMapBase< K, V, Traits >::PersistentValueReference::NewLocal(), FunctionCallbackInfo< T >::NewTarget(), FunctionCallbackInfo< T >::operator[](), PersistentValueMap< K, V, Traits >::SetUnique(), GlobalValueMap< K, V, Traits >::SetUnique(), FunctionCallbackInfo< T >::This(), PropertyCallbackInfo< T >::This(), and MaybeLocal< T >::ToLocalChecked().

MaybeLocal

friend class MaybeLocal

friend

Definition at line 293 of file v8.h.

Referenced by V8InspectorClient::memoryInfo().

Null

Local<Primitive> Null ( Isolate *  isolate )

friend

Definition at line 11111 of file v8.h.

Object

friend class Object

friend

Definition at line 297 of file v8.h.

Persistent

friend class Persistent

friend

Definition at line 290 of file v8.h.

Referenced by Persistent< T, M >::As(), and Persistent< T, M >::Cast().

PersistentBase

friend class PersistentBase

friend

Definition at line 289 of file v8.h.

Referenced by Global< T >::Global(), and Persistent< T, M >::Persistent().

PersistentValueMapBase

friend class PersistentValueMapBase

friend

Definition at line 309 of file v8.h.

PersistentValueVector

friend class PersistentValueVector

friend

Definition at line 310 of file v8.h.

Private

friend class Private

friend

Definition at line 300 of file v8.h.

PropertyCallbackInfo

friend class PropertyCallbackInfo

friend

Definition at line 295 of file v8.h.

ReturnValue

friend class ReturnValue

friend

Definition at line 312 of file v8.h.

Referenced by FunctionCallbackInfo< T >::GetReturnValue(), and PropertyCallbackInfo< T >::GetReturnValue().

String

friend class String

friend

Definition at line 296 of file v8.h.

TracedGlobal

friend class TracedGlobal

friend

Definition at line 314 of file v8.h.

Referenced by TracedGlobal< T >::As().

True

Local<Boolean> True ( Isolate *  isolate )

friend

Definition at line 11120 of file v8.h.

Referenced by Boolean::New().

Undefined

Local<Primitive> Undefined ( Isolate *  isolate )

friend

Definition at line 11102 of file v8.h.

Utils

friend class Utils

friend

Definition at line 287 of file v8.h.

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The documentation for this class was generated from the following file:

• include/v8.h