Just double checked what I was seeing before and I got something wrong. When I get the callback when being used as a prototype, the ClassName isn't set to MyClass, it's just [object object]. But I don't understand why.
On Tuesday, February 16, 2016 at 3:05:57 AM UTC-8, Zac Hansen wrote: > > Here's a reproduction case with pure V8 API code > https://gist.github.com/xaxxon/4bd2abb161ea2253e68d reproduced below > > output: > > In some_function > > Allocating int at 0x7f9c12700520 > > uncasted internal field: 0x7f9c12700520 > > In some_function > > Allocating int at 0x7f9c127004b0 > > uncasted internal field: 0x0 > > > source: > > #include "include/libplatform/libplatform.h" >> #include "include/v8.h" >> class ArrayBufferAllocator : public v8::ArrayBuffer::Allocator { >> public: >> inline virtual void* Allocate(size_t length) override { >> void* data = AllocateUninitialized(length); >> return data == NULL ? data : memset(data, 0, length); >> } >> inline virtual void* AllocateUninitialized(size_t length) override { >> return malloc(length); } >> inline virtual void Free(void* data, size_t) override { free(data); } >> }; >> >> >> void MyClass(const v8::FunctionCallbackInfo<v8::Value> & info) { >> printf("In some_function\n"); >> auto js_object = info.This(); >> int * i = new int(); >> printf("Allocating int at %p\n", i); >> >> js_object->SetInternalField(0, v8::External::New(info.GetIsolate(),i)); >> } >> void do_something(const v8::FunctionCallbackInfo<v8::Value> & info) { >> auto self = info.Holder(); >> auto wrap = v8::Local<v8::External>::Cast(self->GetInternalField(0)); >> printf("uncasted internal field: %p\n", wrap->Value()); >> >> } >> int main(int argc, char ** argv) >> { >> v8::V8::InitializeICU(); >> auto platform = v8::platform::CreateDefaultPlatform(); >> v8::V8::InitializePlatform(platform); >> v8::V8::Initialize(); >> v8::Isolate::CreateParams create_params; >> create_params.array_buffer_allocator = (v8::ArrayBuffer::Allocator >> *) new ArrayBufferAllocator(); >> auto i = v8::Isolate::New(create_params); >> { >> v8::Isolate::Scope is(i); >> v8::HandleScope hs(i); >> auto got = v8::ObjectTemplate::New(i); >> auto ft = v8::FunctionTemplate::New(i, MyClass); >> ft->InstanceTemplate()->SetInternalFieldCount(1); >> got->Set(i, "MyClass", ft); >> auto ft2 = v8::FunctionTemplate::New(i, do_something); >> ft->InstanceTemplate()->Set(i, "do_something", ft2); >> auto c = v8::Context::New(i, nullptr, got); >> v8::Context::Scope cs(c); >> >> auto s = v8::Script::Compile(c, v8::String::NewFromUtf8(i,"new >> MyClass().do_something(); Object.create(new >> MyClass()).do_something();")).ToLocalChecked(); >> (void)s->Run(c); >> } >> } > > > On Tuesday, February 16, 2016 at 2:05:08 AM UTC-8, Zac Hansen wrote: >> >> I have a functiontemplate for the C++ class MyClass, and its objects have >> a MyClass method mymethod in their prototype. >> >> I can create that object in javascript and call it and it calls back into >> the mymethod FunctionTemplate callback: >> >> mc = new MyClass(); mc.mymethod(); <== works fine >> >> >> But if I try to create an object with that as its prototype: >> >> child = Object.create(new MyClass()); child.mymethod(); >> >> >> In the mymethod FunctionTemplate, the object contained in info.Holder() >> (and info.This()) has a .GetInternalField(0) == nullptr; >> >> I added a ClassName to the MyClass FunctionTemplate constructor and in >> the call to >> >> child.mymethod(); >> >> >> if I print out *v8::String::Utf8Value(info.Holder()); in the mymethod >> callback that is about to fail, I get "MyClass". >> >> then I added a data member "int i = rand()" to MyClass and in the >> callback for mymethod() that has a nullptr in its internalfield, if I call >> holder().get(context, "i"), that goes to my c++ getter function and looks >> up the internal field just fine and returns the correct answer. >> >> I'm exceptionally confused. >> >> Thank you for any help. >> >> --Zac >> > -- -- v8-users mailing list [email protected] http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
