1 | ## Nan::Callback
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2 |
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3 | `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.
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4 |
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5 | - <a href="#api_nan_callback"><b><code>Nan::Callback</code></b></a>
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6 |
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7 | <a name="api_nan_callback"></a>
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8 | ### Nan::Callback
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9 |
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10 | ```c++
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11 | class Callback {
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12 | public:
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13 | Callback();
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14 |
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15 | explicit Callback(const v8::Local<v8::Function> &fn);
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16 |
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17 | ~Callback();
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18 |
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19 | bool operator==(const Callback &other) const;
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20 |
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21 | bool operator!=(const Callback &other) const;
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22 |
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23 | v8::Local<v8::Function> operator*() const;
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24 |
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25 | MaybeLocal<v8::Value> operator()(AsyncResource* async_resource,
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26 | v8::Local<v8::Object> target,
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27 | int argc = 0,
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28 | v8::Local<v8::Value> argv[] = 0) const;
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29 |
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30 | MaybeLocal<v8::Value> operator()(AsyncResource* async_resource,
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31 | int argc = 0,
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32 | v8::Local<v8::Value> argv[] = 0) const;
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33 |
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34 | void SetFunction(const v8::Local<v8::Function> &fn);
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35 |
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36 | v8::Local<v8::Function> GetFunction() const;
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37 |
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38 | bool IsEmpty() const;
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39 |
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40 | void Reset(const v8::Local<v8::Function> &fn);
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41 |
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42 | void Reset();
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43 |
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44 | MaybeLocal<v8::Value> Call(v8::Local<v8::Object> target,
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45 | int argc,
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46 | v8::Local<v8::Value> argv[],
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47 | AsyncResource* async_resource) const;
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48 | MaybeLocal<v8::Value> Call(int argc,
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49 | v8::Local<v8::Value> argv[],
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50 | AsyncResource* async_resource) const;
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51 |
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52 | // Deprecated versions. Use the versions that accept an async_resource instead
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53 | // as they run the callback in the correct async context as specified by the
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54 | // resource. If you want to call a synchronous JS function (i.e. on a
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55 | // non-empty JS stack), you can use Nan::Call instead.
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56 | v8::Local<v8::Value> operator()(v8::Local<v8::Object> target,
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57 | int argc = 0,
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58 | v8::Local<v8::Value> argv[] = 0) const;
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59 |
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60 | v8::Local<v8::Value> operator()(int argc = 0,
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61 | v8::Local<v8::Value> argv[] = 0) const;
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62 | v8::Local<v8::Value> Call(v8::Local<v8::Object> target,
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63 | int argc,
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64 | v8::Local<v8::Value> argv[]) const;
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65 |
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66 | v8::Local<v8::Value> Call(int argc, v8::Local<v8::Value> argv[]) const;
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67 | };
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68 | ```
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69 |
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70 | Example usage:
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71 |
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72 | ```c++
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73 | v8::Local<v8::Function> function;
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74 | Nan::Callback callback(function);
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75 | callback.Call(0, 0);
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76 | ```
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