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77 lines
2.3 KiB
77 lines
2.3 KiB
4 years ago
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# AsyncContext
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The [Napi::AsyncWorker](async_worker.md) class may not be appropriate for every
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scenario. When using any other async mechanism, introducing a new class
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`Napi::AsyncContext` is necessary to ensure an async operation is properly
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tracked by the runtime. The `Napi::AsyncContext` class can be passed to
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[Napi::Function::MakeCallback()](function.md) method to properly restore the
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correct async execution context.
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## Methods
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### Constructor
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Creates a new `Napi::AsyncContext`.
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```cpp
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explicit Napi::AsyncContext::AsyncContext(napi_env env, const char* resource_name);
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```
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- `[in] env`: The environment in which to create the `Napi::AsyncContext`.
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- `[in] resource_name`: Null-terminated strings that represents the
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identifier for the kind of resource that is being provided for diagnostic
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information exposed by the `async_hooks` API.
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### Constructor
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Creates a new `Napi::AsyncContext`.
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```cpp
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explicit Napi::AsyncContext::AsyncContext(napi_env env, const char* resource_name, const Napi::Object& resource);
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```
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- `[in] env`: The environment in which to create the `Napi::AsyncContext`.
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- `[in] resource_name`: Null-terminated strings that represents the
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identifier for the kind of resource that is being provided for diagnostic
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information exposed by the `async_hooks` API.
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- `[in] resource`: Object associated with the asynchronous operation that
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will be passed to possible `async_hooks`.
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### Destructor
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The `Napi::AsyncContext` to be destroyed.
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```cpp
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virtual Napi::AsyncContext::~AsyncContext();
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```
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## Operator
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```cpp
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Napi::AsyncContext::operator napi_async_context() const;
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```
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Returns the N-API `napi_async_context` wrapped by the `Napi::AsyncContext`
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object. This can be used to mix usage of the C N-API and node-addon-api.
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## Example
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```cpp
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#include "napi.h"
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void MakeCallbackWithAsyncContext(const Napi::CallbackInfo& info) {
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Napi::Function callback = info[0].As<Napi::Function>();
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Napi::Object resource = info[1].As<Napi::Object>();
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// Creat a new async context instance.
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Napi::AsyncContext context(info.Env(), "async_context_test", resource);
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// Invoke the callback with the async context instance.
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callback.MakeCallback(Napi::Object::New(info.Env()),
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std::initializer_list<napi_value>{}, context);
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// The async context instance is automatically destroyed here because it's
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// block-scope like `Napi::HandleScope`.
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}
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```
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