使用 Rcpp 模块公开带有引用参数的 C++ 类方法时出错 [英] Error exposing c++ class method with reference parameter using Rcpp modules
问题描述
我的目标是构建一个数据集类和一个模型类,并将它们都暴露给 R.模型类有一个 train()
方法,它引用一个数据集实例,并且这似乎是我问题的根源.这是这个样子
My goal is to build a dataset class and a model class, and expose both of them to R. The model class has a train()
method that takes a reference to a dataset instance, and this seems to be at the root of my issue. Here's what this looks like
//glue.cpp
#include <Rcpp.h>
class MyData
{
public:
MyData() = default;
};
class MyModel
{
public:
MyModel() = default;
void train(const MyData& data) { Rcpp::Rcout << "training model... "; };
};
// Expose MyData
RCPP_MODULE(MyData){
Rcpp::class_<MyData>("MyData")
.constructor()
;
}
// Expose MyModel
RCPP_MODULE(MyModel){
Rcpp::class_<MyModel>("MyModel")
.constructor()
.method("train", &MyModel::train)
;
}
(我应该注意到这个文件glue.cpp 嵌入在一个R 包中.)当我删除这一行时,.method("train", &MyModel::train)
,我可以通过 pkgbuild::compile_dll()
编译它而不会出错.有了它,我得到了下面令人讨厌的错误
(I should note that this file, glue.cpp, is embedded in an R package.) When I remove this line, .method("train", &MyModel::train)
, I can compile this without error via pkgbuild::compile_dll()
. With it, I get the nasty error below
─ installing *source* package ‘SimpleCppModel’ ...
** libs
clang++ -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I/usr/local/include -std=c++14 -fPIC -Wall -g -O2 -c RcppExports.cpp -o RcppExports.o
clang++ -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I/usr/local/include -std=c++14 -fPIC -Wall -g -O2 -c glue.cpp -o glue.o
In file included from glue.cpp:3:
In file included from /Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp.h:27:
In file included from /Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/RcppCommon.h:168:
In file included from /Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/as.h:25:
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/internal/Exporter.h:31:28: error: no matching constructor for initialization of 'MyData'
Exporter( SEXP x ) : t(x){}
^ ~
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/as.h:87:41: note: in instantiation of member function 'Rcpp::traits::Exporter<MyData>::Exporter' requested here
::Rcpp::traits::Exporter<T> exporter(x);
^
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/as.h:152:26: note: in instantiation of function template specialization 'Rcpp::internal::as<MyData>' requested here
return internal::as<T>(x, typename traits::r_type_traits<T>::r_category());
^
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/InputParameter.h:72:54: note: in instantiation of function template specialization 'Rcpp::as<MyData>' requested here
ConstReferenceInputParameter(SEXP x_) : obj( as<T>(x_) ){}
^
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/module/Module_generated_CppMethod.h:129:58: note: in instantiation of member function 'Rcpp::ConstReferenceInputParameter<MyData>::ConstReferenceInputParameter' requested here
typename Rcpp::traits::input_parameter<U0>::type x0(args[0]);
^
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/module/Module_generated_CppMethod.h:127:5: note: in instantiation of member function 'Rcpp::CppMethod1<MyModel, void, const MyData &>::operator()' requested here
CppMethod1( Method m) : method_class(), met(m) {}
^
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/module/Module_generated_method.h:59:27: note: in instantiation of member function 'Rcpp::CppMethod1<MyModel, void, const MyData &>::CppMethod1' requested here
AddMethod( name_, new CppMethod1<Class,RESULT_TYPE,U0>(fun), valid, docstring);
^
glue.cpp:30:4: note: in instantiation of function template specialization 'Rcpp::class_<MyModel>::method<void, const MyData &>' requested here
.method("train", &MyModel::train)
^
glue.cpp:5:7: note: candidate constructor (the implicit copy constructor) not viable: cannot convert argument of incomplete type 'SEXP' (aka 'SEXPREC *') to 'const MyData' for 1st argument
class MyData
^
glue.cpp:5:7: note: candidate constructor (the implicit move constructor) not viable: cannot convert argument of incomplete type 'SEXP' (aka 'SEXPREC *') to 'MyData' for 1st argument
glue.cpp:8:3: note: candidate constructor not viable: requires 0 arguments, but 1 was provided
MyData() = default;
^
1 error generated.
make: *** [glue.o] Error 1
ERROR: compilation failed for package ‘SimpleCppModel’
─ removing ‘/private/var/folders/dn/9lp6j6j14t1137ftnnk27wyw0000gn/T/RtmpBqDLoF/devtools_install_4d775ed17ea2/SimpleCppModel’
Error in processx::run(bin, args = real_cmdargs, stdout_line_callback = real_callback(stdout), :
System command error
是什么?
推荐答案
正如 Dirk 在评论中提到的,您将需要 as<>
和 wrap
专业化我的数据
.在您的情况下,您可以使用扩展 Rcpp"小插图中最简单的解决方案:RCPP_EXPOSED_CLASS
.当你包含来自 Rcpp 的头时你必须小心:
As mentioned by Dirk in the comments, you will need as<>
and wrap
specializations for MyData
. In your case, you can use the easiest solution from the "Extending Rcpp" vignette: RCPP_EXPOSED_CLASS
. You just have to be careful when you include which header from Rcpp:
#include <Rcpp.h>
class MyData
{
public:
MyData() = default;
};
RCPP_EXPOSED_CLASS(MyData)
class MyModel
{
public:
MyModel() = default;
void train(const MyData& data) { Rcpp::Rcout << "training model... " << std::endl; };
};
// Expose MyData
RCPP_MODULE(MyData){
Rcpp::class_<MyData>("MyData")
.constructor()
;
}
// Expose MyModel
RCPP_MODULE(MyModel){
Rcpp::class_<MyModel>("MyModel")
.constructor()
.method("train", &MyModel::train)
;
}
/***R
myData <- new(MyData)
myModel <- new(MyModel)
myModel$train(myData)
*/
正如您在回答中发现的那样,这甚至在之后有效,包括Rcpp.h
.不过,浏览上面提到的画廊文章和小插图仍然很有意义.
As you found out in your answer, this even works after including Rcpp.h
.
It still makes sense to go through the mentioned gallery article as well the vignette, though.
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