我有两个简单的类A
和B
,我想将它们暴露在node.js的本地模块中。直接可以创建A
,但只能通过调用A::foo()
来创建B
。
class Internal {};
class B {
public:
Internal internal;
explicit B(Internal internal):internal(internal){}
};
class A {
public:
A() : internal() {};
B foo() { return B(internal); }
private:
Internal internal;
};
我希望能够编写以下内容:
const M = require('node_nan_minimal');
const a = new M.A();
const b = a.foo();
为了实现这一点,我正在创建两个继承自
Nan::ObjectWrap
的包装类。class AWrapper : public Nan::ObjectWrap { ... }
class BWrapper : public Nan::ObjectWrap { ... }
每个都包含一个实例
A
或者 B
。通过这些,我可以在javascript中创建一个类型为A的对象,但是我在实现AWrapper::foo
时遇到一些问题。static NAN_METHOD(foo) {
AWrapper* obj = Nan::ObjectWrap::Unwrap<AWrapper>(info.Holder());
B b = obj->a_.foo();
BWrapper * result = new BWrapper(b);
// Something to get a B object to javascript
// ...
// info.GetReturnValue().Set(result->Wrap());
// ...
// doesn't work - so what should it be?
}
我该怎么做才能使这个函数起作用?
这个 .cc 文件的完整代码如下:
#include <node.h>
#include <nan.h>
class Internal {
};
class B {
public:
Internal internal;
explicit B(Internal internal):internal(internal){}
};
class A {
public:
A() : internal() {};
B foo() { return B(internal); }
private:
Internal internal;
};
class BWrapper : public Nan::ObjectWrap {
public:
B b_;
explicit BWrapper(B b) : b_(b) {}
~BWrapper() {}
};
class AWrapper : public Nan::ObjectWrap {
public:
A a_;
explicit AWrapper(A a) : a_(a) {}
~AWrapper() {}
static void register_class(Nan::ADDON_REGISTER_FUNCTION_ARGS_TYPE target) {
v8::Local<v8::FunctionTemplate> tpl = Nan::New<v8::FunctionTemplate>(New);
tpl->SetClassName(Nan::New("A").ToLocalChecked());
tpl->InstanceTemplate()->SetInternalFieldCount(1);
Nan::SetPrototypeMethod(tpl, "foo", foo);
constructor().Reset(Nan::GetFunction(tpl).ToLocalChecked());
Nan::Set(target, Nan::New("A").ToLocalChecked(), Nan::GetFunction(tpl).ToLocalChecked());
}
private:
static NAN_METHOD(New) {
if (info.IsConstructCall()) {
A a;
AWrapper *obj = new AWrapper(a);
obj->Wrap(info.This());
info.GetReturnValue().Set(info.This());
} else {
const int argc = 1;
v8::Local<v8::Value> argv[argc] = {info[0]};
v8::Local<v8::Function> cons = Nan::New(constructor());
info.GetReturnValue().Set(cons->NewInstance(argc, argv));
}
}
static NAN_METHOD(foo) {
AWrapper* obj = Nan::ObjectWrap::Unwrap<AWrapper>(info.Holder());
B b = obj->a_.foo();
BWrapper * result = new BWrapper(b);
// Something to get a B object to javascript
//...
//info.GetReturnValue().Set(result->Wrap());
}
static inline Nan::Persistent<v8::Function> & constructor() {
static Nan::Persistent<v8::Function> my_constructor;
return my_constructor;
}
};
NAN_MODULE_INIT(InitModule) {
AWrapper::register_class(target);
}
NODE_MODULE(NODE_GYP_MODULE_NAME, InitModule);
完整的示例代码存储库可以在https://github.com/mikeando/node_nan_minimal找到,您可以克隆该存储库,然后使用npm install
构建。