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Add example/api to use ThreadSafeFunction with optional callback param #544
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I think it would make more sense to add a new signature without the
Functionargument. I feel like that's more intuitive. We are currently working on a fix to add a copy constructor, so odds are we could add this as well.Reacted by Chengzhong Wu and Michael DawsonSooo I think implementing a new constructor will blow up the number of constructors we have. We currently have thirteen
::Newoverloads, and if making theFunctionoptional by removing it, we would add thirteen more. I dunno, we will discuss in next napi meetingI would like to use this issue to highlight all issues with TSFN constructors. I point out the ambiguity between the TSFN::New with
Finalizer + FinalizerDataTypeandContextType + Finalizer:struct TestData { // Native Promise returned to JavaScript Promise::Deferred deferred; // List of threads created for test. This list only ever accessed via main // thread. vector<thread> threads = {}; ThreadSafeFunction tsfn = ThreadSafeFunction(); }; void FinalizerCallback(Napi::Env env, TestData* finalizeData){ for (size_t i = 0; i < finalizeData->threads.size(); ++i) { finalizeData->threads[i].join(); } finalizeData->deferred.Resolve(Boolean::New(env,true)); delete finalizeData; } static Value TestAcquire(const CallbackInfo& info) { // .... TestData *testData = new TestData({ Promise::Deferred::New(env) }); testData->tsfn = ThreadSafeFunction::New(env, cb, "Test", 0, 1, FinalizerCallback, testData); // ... }
The call to
Newis ambiguous:./threadsafe_function/threadsafe_function_sum.cc:142:20: error: call to 'New' is ambiguous testData->tsfn = ThreadSafeFunction::New(env, cb, "Test", 0, 1, FinalizerCallback, testData); ^~~~~~~~~~~~~~~~~~~~~~~ /Users/kevineady/Documents/Projects/node-addon-api/napi-inl.h:3839:47: note: candidate function [with ResourceString = const char *, Finalizer = void (*)(Napi::Env, (anonymous namespace)::TestData *), FinalizerDataType = (anonymous namespace)::TestData] inline ThreadSafeFunction ThreadSafeFunction::New(napi_env env, ^ /Users/kevineady/Documents/Projects/node-addon-api/napi-inl.h:3852:47: note: candidate function [with ResourceString = const char *, ContextType = void (Napi::Env, (anonymous namespace)::TestData *), Finalizer = (anonymous namespace)::TestData *] inline ThreadSafeFunction ThreadSafeFunction::New(napi_env env, ^ 1 error generated. make: *** [Debug/obj.target/binding/threadsafe_function/threadsafe_function_sum.o] Error 1I can solve this issue by explicitly using
std::functionlike so:testData->tsfn = ThreadSafeFunction::New(env, cb, "Test", 0, 1, std::function<void (Napi::Env env, TestData* finalizeData)>(FinalizerCallback), testData);
This issue is stale because it has been open many days with no activity. It will be closed soon unless the stale label is removed or a comment is made.
@KevinEady , @legendecas should do we still need this issue?
@legendecas what's your take, I don't have a strong opinion one way or the other.
I may say that this may not be the way ThreadSafeFunction recommended to use. I'm closing since I did not find any strong use case on this. Even cases may arise, documenting that the callback can be empty sounds enough to me.
Since nodejs/node#27791 has been landed, there might be some use cases on node-addon-api to use
Napi::ThreadSafeFunctionwith optional callback parameter.Approaches might be adding an example of how to use existing
Napi::ThreadSafeFunction::Newlike:(is there a more intuitive one?)
Or add a new API which make the callback omitted: