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node_modules/nan/doc/callback.md 2.57 KB
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  ## Nan::Callback
  
  `Nan::Callback` makes it easier to use `v8::Function` handles as callbacks. A class that wraps a `v8::Function` handle, protecting it from garbage collection and making it particularly useful for storage and use across asynchronous execution.
  
   - <a href="#api_nan_callback"><b><code>Nan::Callback</code></b></a>
  
  <a name="api_nan_callback"></a>
  ### Nan::Callback
  
  ```c++
  class Callback {
   public:
    Callback();
  
    explicit Callback(const v8::Local<v8::Function> &fn);
  
    ~Callback();
  
    bool operator==(const Callback &other) const;
  
    bool operator!=(const Callback &other) const;
  
    v8::Local<v8::Function> operator*() const;
  
    MaybeLocal<v8::Value> operator()(AsyncResource* async_resource,
                                     v8::Local<v8::Object> target,
                                     int argc = 0,
                                     v8::Local<v8::Value> argv[] = 0) const;
  
    MaybeLocal<v8::Value> operator()(AsyncResource* async_resource,
                                     int argc = 0,
                                     v8::Local<v8::Value> argv[] = 0) const;
  
    void SetFunction(const v8::Local<v8::Function> &fn);
  
    v8::Local<v8::Function> GetFunction() const;
  
    bool IsEmpty() const;
  
    void Reset(const v8::Local<v8::Function> &fn);
  
    void Reset();
  
    MaybeLocal<v8::Value> Call(v8::Local<v8::Object> target,
                              int argc,
                              v8::Local<v8::Value> argv[],
                              AsyncResource* async_resource) const;
    MaybeLocal<v8::Value> Call(int argc,
                               v8::Local<v8::Value> argv[],
                               AsyncResource* async_resource) const;
  
    // Deprecated versions. Use the versions that accept an async_resource instead
    // as they run the callback in the correct async context as specified by the
    // resource. If you want to call a synchronous JS function (i.e. on a
    // non-empty JS stack), you can use Nan::Call instead.
    v8::Local<v8::Value> operator()(v8::Local<v8::Object> target,
                                    int argc = 0,
                                    v8::Local<v8::Value> argv[] = 0) const;
  
    v8::Local<v8::Value> operator()(int argc = 0,
                                    v8::Local<v8::Value> argv[] = 0) const;
    v8::Local<v8::Value> Call(v8::Local<v8::Object> target,
                              int argc,
                              v8::Local<v8::Value> argv[]) const;
  
    v8::Local<v8::Value> Call(int argc, v8::Local<v8::Value> argv[]) const;
  };
  ```
  
  Example usage:
  
  ```c++
  v8::Local<v8::Function> function;
  Nan::Callback callback(function);
  callback.Call(0, 0);
  ```