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75 lines
2.0 KiB
75 lines
2.0 KiB
4 years ago
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# Promise
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The `Napi::Promise` class, along with its `Napi::Promise::Deferred` class, implement the ability to create, resolve, and reject Promise objects.
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The basic approach is to create a `Napi::Promise::Deferred` object and return to your caller the value returned by the `Napi::Promise::Deferred::Promise` method. For example:
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```cpp
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Napi::Value YourFunction(const Napi::CallbackInfo& info) {
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// your code goes here...
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Napi::Promise::Deferred deferred = Napi::Promise::Deferred::New(info.Env());
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// deferred needs to survive this call...
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return deferred.Promise();
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}
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```
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Later, when the asynchronous process completes, call either the `Resolve` or `Reject` method on the `Napi::Promise::Deferred` object created earlier:
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```cpp
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deferred.Resolve(String::New(info.Env(), "OK"));
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```
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## Promise::Deferred Methods
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### Factory Method
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```cpp
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static Napi::Promise::Deferred Napi::Promise::Deferred::New(napi_env env);
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```
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* `[in] env`: The `napi_env` environment in which to create the `Napi::Promise::Deferred` object.
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### Constructor
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```cpp
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Napi::Promise::Deferred(napi_env env);
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```
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* `[in] env`: The `napi_env` environment in which to construct the `Napi::Promise::Deferred` object.
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### Env
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```cpp
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Napi::Env Napi::Promise::Deferred::Env() const;
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```
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Returns the Env environment this `Napi::Promise::Deferred` object is associated with.
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### Promise
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```cpp
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Napi::Promise Napi::Promise::Deferred::Promise() const;
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```
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Returns the `Napi::Promise` object held by the `Napi::Promise::Deferred` object.
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### Resolve
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```cpp
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void Napi::Promise::Deferred::Resolve(napi_value value) const;
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```
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Resolves the `Napi::Promise` object held by the `Napi::Promise::Deferred` object.
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* `[in] value`: The N-API primitive value with which to resolve the `Napi::Promise`.
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### Reject
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```cpp
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void Napi::Promise::Deferred::Reject(napi_value value) const;
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```
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Rejects the Promise object held by the `Napi::Promise::Deferred` object.
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* `[in] value`: The N-API primitive value with which to reject the `Napi::Promise`.
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