8.0 KiB
Property Descriptor
A Napi::Object can be assigned
properites via its DefineProperty and DefineProperties
functions, which take PropertyDescrptor(s) as their parameters. The
Napi::PropertyDescriptor can contain either values or
functions, which are then assigned to the Napi::Object.
Note that a single instance of a Napi::PropertyDescriptor
class can only contain either one value, or at most two functions.
PropertyDescriptors can only be created through the class methods Accessor, Function, or Value, each of which return a new static
instance of a Napi::PropertyDescriptor.
Example
#include <napi.h>
using namespace Napi;
Value TestGetter(const CallbackInfo& info) {
return Boolean::New(info.Env(), testValue);
}
void TestSetter(const CallbackInfo& info) {
testValue = info[0].As<Boolean>();
}
Value TestFunction(const CallbackInfo& info) {
return Boolean::New(info.Env(), true);
}
Void Init(Env env) {
// Create an object.
Object obj = Object::New(env);
// Accessor
PropertyDescriptor pd1 = PropertyDescriptor::Accessor(env,
obj,
"pd1",
TestGetter);
PropertyDescriptor pd2 = PropertyDescriptor::Accessor(env,
obj,
"pd2",
TestGetter,
TestSetter);
// Function
PropertyDescriptor pd3 = PropertyDescriptor::Function(env,
"function",
TestFunction);
// Value
Boolean true_bool = Boolean::New(env, true);
PropertyDescriptor pd4 =
PropertyDescriptor::Value("boolean value",
Napi::Boolean::New(env, true),
napi_writable);
// Assign properties to the object.
obj.DefineProperties({pd1, pd2, pd3, pd4});
}Methods
Constructor
Napi::PropertyDescriptor::PropertyDescriptor (napi_property_descriptor desc);[in] desc: A PropertyDescriptor that is needed in order to create another PropertyDescriptor.
Accessor
static Napi::PropertyDescriptor Napi::PropertyDescriptor::Accessor (___ name,
Getter getter,
napi_property_attributes attributes = napi_default,
void *data = nullptr);[in] name: The name used for the getter function.[in] getter: A getter function.[in] attributes: Potential attributes for the getter function.[in] data: A pointer to data of any type, default is a null pointer.
Returns a PropertyDescriptor that contains a function.
The name of the property can be any of the following types: -
const char* - const std::string & -
napi_value value - Napi::Name
This signature is deprecated. It will result in a memory leak if used.
static Napi::PropertyDescriptor Napi::PropertyDescriptor::Accessor (
Napi::Env env,
Napi::Object object,
___ name,
Getter getter,
napi_property_attributes attributes = napi_default,
void *data = nullptr);[in] env: The environemnt in which to create this accessor.[in] object: The object on which the accessor will be defined.[in] name: The name used for the getter function.[in] getter: A getter function.[in] attributes: Potential attributes for the getter function.[in] data: A pointer to data of any type, default is a null pointer.
Returns a Napi::PropertyDescriptor that contains a
Getter accessor.
The name of the property can be any of the following types: -
const char* - const std::string & -
Napi::Name
static Napi::PropertyDescriptor Napi::PropertyDescriptor::Accessor (___ name,
Getter getter,
Setter setter,
napi_property_attributes attributes = napi_default,
void *data = nullptr);[in] name: The name of the getter and setter function.[in] getter: The getter function.[in] setter: The setter function.[in] attributes: Potential attributes for the getter function.[in] data: A pointer to data of any type, default is a null pointer.
Returns a Napi::PropertyDescriptor that contains a
Getter and Setter function.
The name of the property can be any of the following types: -
const char* - const std::string & -
napi_value value - Napi::Name
This signature is deprecated. It will result in a memory leak if used.
static Napi::PropertyDescriptor Napi::PropertyDescriptor::Accessor (
Napi::Env env,
Napi::Object object,
___ name,
Getter getter,
Setter setter,
napi_property_attributes attributes = napi_default,
void *data = nullptr);[in] env: The environemnt in which to create this accessor.[in] object: The object on which the accessor will be defined.[in] name: The name of the getter and setter function.[in] getter: The getter function.[in] setter: The setter function.[in] attributes: Potential attributes for the getter function.[in] data: A pointer to data of any type, default is a null pointer.
Returns a Napi::PropertyDescriptor that contains a
Getter and Setter function.
The name of the property can be any of the following types: -
const char* - const std::string & -
Napi::Name
Function
static Napi::PropertyDescriptor Napi::PropertyDescriptor::Function (___ name,
Callable cb,
napi_property_attributes attributes = napi_default,
void *data = nullptr);[in] name: The name of the Callable function.[in] cb: The function[in] attributes: Potential attributes for the getter function.[in] data: A pointer to data of any type, default is a null pointer.
Returns a Napi::PropertyDescriptor that contains a
callable Napi::Function.
The name of the property can be any of the following types: -
const char* - const std::string & -
napi_value value - Napi::Name
This signature is deprecated. It will result in a memory leak if used.
static Napi::PropertyDescriptor Napi::PropertyDescriptor::Function (
Napi::Env env,
___ name,
Callable cb,
napi_property_attributes attributes = napi_default,
void *data = nullptr);[in] env: The environment in which to create this accessor.[in] name: The name of the Callable function.[in] cb: The function[in] attributes: Potential attributes for the getter function.[in] data: A pointer to data of any type, default is a null pointer.
Returns a Napi::PropertyDescriptor that contains a
callable Napi::Function.
The name of the property can be any of the following types: -
const char* - const std::string & -
Napi::Name
Value
static Napi::PropertyDescriptor Napi::PropertyDescriptor::Value (___ name,
napi_value value,
napi_property_attributes attributes = napi_default);The name of the property can be any of the following types: -
const char* - const std::string & -
napi_value value - Napi::Name
Related Information
napi_property_attributes
napi_property_attributes are flags used to indicate to
JavaScript certain permissions that the property is meant to have. The
following are the flag options: - napi_default, - napi_writable, -
napi_enumerable, - napi_configurable For more information on the flags
and on napi_property_attributes, please read the documentation here.