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112 lines
2.9 KiB
112 lines
2.9 KiB
4 years ago
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# Reference (template)
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Holds a counted reference to a [`Napi::Value`](value.md) object; initially a weak reference unless otherwise specified, may be changed to/from a strong reference by adjusting the refcount.
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The referenced `Napi::Value` is not immediately destroyed when the reference count is zero; it is merely then eligible for garbage-collection if there are no other references to the `Napi::Value`.
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`Napi::Reference` objects allocated in static space, such as a global static instance, must call the `SuppressDestruct` method to prevent its destructor, running at program shutdown time, from attempting to reset the reference when the environment is no longer valid.
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The following classes inherit, either directly or indirectly, from `Napi::Reference`:
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* [`Napi::ObjectWrap`](object_wrap.md)
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* [`Napi::ObjectReference`](object_reference.md)
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* [`Napi::FunctionReference`](function_reference.md)
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## Methods
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### Factory Method
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```cpp
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static Napi::Reference<T> Napi::Reference::New(const T& value, uint32_t initialRefcount = 0);
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```
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* `[in] value`: The value which is to be referenced.
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* `[in] initialRefcount`: The initial reference count.
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### Empty Constructor
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```cpp
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Napi::Reference::Reference();
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```
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Creates a new _empty_ `Napi::Reference` instance.
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### Constructor
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```cpp
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Napi::Reference::Reference(napi_env env, napi_value value);
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```
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* `[in] env`: The `napi_env` environment in which to construct the `Napi::Reference` object.
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* `[in] value`: The N-API primitive value to be held by the `Napi::Reference`.
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### Env
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```cpp
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Napi::Env Napi::Reference::Env() const;
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```
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Returns the `Napi::Env` value in which the `Napi::Reference` was instantiated.
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### IsEmpty
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```cpp
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bool Napi::Reference::IsEmpty() const;
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```
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Determines whether the value held by the `Napi::Reference` is empty.
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### Value
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```cpp
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T Napi::Reference::Value() const;
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```
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Returns the value held by the `Napi::Reference`.
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### Ref
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```cpp
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uint32_t Napi::Reference::Ref();
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```
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Increments the reference count for the `Napi::Reference` and returns the resulting reference count. Throws an error if the increment fails.
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### Unref
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```cpp
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uint32_t Napi::Reference::Unref();
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```
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Decrements the reference count for the `Napi::Reference` and returns the resulting reference count. Throws an error if the decrement fails.
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### Reset (Empty)
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```cpp
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void Napi::Reference::Reset();
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```
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Sets the value held by the `Napi::Reference` to be empty.
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### Reset
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```cpp
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void Napi::Reference::Reset(const T& value, uint32_t refcount = 0);
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```
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* `[in] value`: The value which is to be referenced.
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* `[in] initialRefcount`: The initial reference count.
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Sets the value held by the `Napi::Reference`.
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### SuppressDestruct
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```cpp
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void Napi::Reference::SuppressDestruct();
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```
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Call this method on a `Napi::Reference` that is declared as static data to prevent its destructor, running at program shutdown time, from attempting to reset the reference when the environment is no longer valid.
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