如何解决C++ 自定义类继承特征初始值设定项列表
我正在尝试制作一个从 Eigen 的 vector 3 继承的自定义 Vector3。
using Vector3 = Eigen::Vector3d;
enum class CustomEnum
{
E1,E2 E3,E4,};
class CustomVector3 : public Vector3
{
public:
// Taken from here: https://eigen.tuxfamily.org/dox/TopicCustomizing_InheritingMatrix.html
CustomVector3():Vector3(){}
template<typename OtherDerived>
CustomVector3(const Eigen::MatrixBase<OtherDerived>& other) : Vector3(other) {}
// Initializer Constructor
template<typename OtherDerived>
CustomVector3(const std::initializer_list<OtherDerived>& other) : Vector3(other) {}
template<typename OtherDerived>
CustomVector3& operator=(const Eigen::MatrixBase<OtherDerived>& other){
this->Vector3::operator=(other);
return *this;
}
CustomEnum e = CustomEnum::E1;
};
我们的目标是做到以下几点:
TEST_CASE("Initalizer List Test")
{
CustomVector3 vec = {1.1,2.2,3.3};
CHECK(vec.x() == 1.1);
CHECK(vec.y() == 2.2);
CHECK(vec.z() == 3.3);
assert(vec.frame == CustomEnum::E1);
}
没有初始化构造函数,我可以执行以下操作,但不是我上面提到的目标:
Vector3 data = {1.1,3.3};
CustomVector3 framedData = data;
使用初始化构造函数时,我收到以下编译错误消息(我在代码中将其称为 FramedVector3,但为了清楚起见,我在本文中将其称为 CustomVector3):
/usr/include/eigen3/Eigen/src/Core/Matrix.h: In instantiation of ‘Eigen::Matrix<_Scalar,_Rows,_Cols,_Options,_MaxRows,_MaxCols>::Matrix(const T&) [with T = std::initializer_list<double>; _Scalar = double; int _Rows = 3; int _Cols = 1; int _Options = 0; int _MaxRows = 3; int _MaxCols = 1]’:
/home/seedship/uavAP/include/uavAP/Core/FramedVector3.h:23:81: required from ‘FramedVector3::FramedVector3(const std::initializer_list<_Tp>&) [with OtherDerived = double]’
/home/seedship/uavAP/include/uavAP/Core/SensorData.h:128:38: required from here
/usr/include/eigen3/Eigen/src/Core/Matrix.h:294:31: error: no matching function for call to ‘Eigen::Matrix<double,3,1>::_init1<std::initializer_list<double> >(const std::initializer_list<double>&)’
294 | Base::template _init1<T>(x);
| ~~~~~~~~~~~~~~~~~~~~~~~~^~~
In file included from /usr/include/eigen3/Eigen/Core:462,from /usr/include/eigen3/Eigen/Dense:1,from /usr/local/include/cpsCore/Utilities/LinearAlgebra.h:13,from /home/seedship/uavAP/include/uavAP/Core/FramedVector3.h:9,from /home/seedship/uavAP/include/uavAP/Core/SensorData.h:11,from /home/seedship/uavAP/include/uavAP/Core/Orientation/ENU.h:8,from /home/seedship/uavAP/src/Core/Orientation/ENU.cpp:5:
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h:774:30: note: candidate: ‘void Eigen::PlainObjectBase<Derived>::_init1(Eigen::Index,typename Eigen::internal::enable_if<(((typename Eigen::internal::dense_xpr_base<Derived>::type::SizeAtCompileTime != 1) || (! Eigen::internal::is_convertible<T,typename Eigen::internal::traits<T>::Scalar>::value)) && ((! Eigen::internal::is_same<typename Eigen::internal::traits<T>::XprKind,Eigen::ArrayXpr>::value) || (typename Eigen::internal::dense_xpr_base<Derived>::type::SizeAtCompileTime == Eigen::Dynamic))),T>::type*) [with T = std::initializer_list<double>; Derived = Eigen::Matrix<double,1>; Eigen::Index = long int; typename Eigen::internal::enable_if<(((typename Eigen::internal::dense_xpr_base<Derived>::type::SizeAtCompileTime != 1) || (! Eigen::internal::is_convertible<T,T>::type = std::initializer_list<double>]’
774 | EIGEN_STRONG_INLINE void _init1(Index size,typename internal::enable_if< (Base::SizeAtCompileTime!=1 || !internal::is_convertible<T,Scalar>::value)
| ^~~~~~
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h:774:43: note: no known conversion for argument 1 from ‘const std::initializer_list<double>’ to ‘Eigen::Index’ {aka ‘long int’}
774 | EIGEN_STRONG_INLINE void _init1(Index size,Scalar>::value)
| ~~~~~~^~~~
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h:788:30: note: candidate: ‘template<class T> void Eigen::PlainObjectBase<Derived>::_init1(const Scalar&,typename Eigen::internal::enable_if<((typename Eigen::internal::dense_xpr_base<Derived>::type::SizeAtCompileTime == 1) && Eigen::internal::is_convertible<T,typename Eigen::internal::traits<T>::Scalar>::value),T>::type*) [with T = T; Derived = Eigen::Matrix<double,1>]’
788 | EIGEN_STRONG_INLINE void _init1(const Scalar& val0,typename internal::enable_if<Base::SizeAtCompileTime==1 && internal::is_convertible<T,Scalar>::value,T>::type* = 0)
| ^~~~~~
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h:788:30: note: template argument deduction/substitution failed:
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h: In substitution of ‘template<class T> void Eigen::PlainObjectBase<Eigen::Matrix<double,1> >::_init1<T>(const Scalar&,typename Eigen::internal::enable_if<((Eigen::MatrixBase<Eigen::Matrix<double,1> >::SizeAtCompileTime == 1) && Eigen::internal::is_convertible<T,double>::value),T>::type*) [with T = std::initializer_list<double>]’:
/usr/include/eigen3/Eigen/src/Core/Matrix.h:294:31: required from ‘Eigen::Matrix<_Scalar,_MaxCols>::Matrix(const T&) [with T = std::initializer_list<double>; _Scalar = double; int _Rows = 3; int _Cols = 1; int _Options = 0; int _MaxRows = 3; int _MaxCols = 1]’
/home/seedship/uavAP/include/uavAP/Core/FramedVector3.h:23:81: required from ‘FramedVector3::FramedVector3(const std::initializer_list<_Tp>&) [with OtherDerived = double]’
/home/seedship/uavAP/include/uavAP/Core/SensorData.h:128:38: required from here
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h:788:30: error: invalid use of incomplete type ‘struct Eigen::internal::enable_if<false,std::initializer_list<double> >’
[Truncated for brevity]
谁能解释我遗漏了什么?我很困惑为什么赋值运算符有效,而不是构造函数。这发生在 Eigen 3.3.9-1 和 eigen-git 上。
更新:也许这个问题是特定于库的,所以我问了 Eigen gitlab 项目 (https://gitlab.com/libeigen/eigen/-/issues/2192)
解决方法
您需要使用额外的一对括号。模板化这个构造函数也没有意义,因为模板参数类型需要匹配特征向量的标量类型,如果你希望标量类型是可配置的,你需要模板整个类。
总结
CustomVector3(const std::initializer_list<double>& other) : Vector3({other}) {}
是正确的方法。原因是 Eigen::Vector3d
是 Eigen::Matrix<double,3,1>
的 typedef。矩阵的初始化列表构造函数需要处理多行和多列,因此具有签名
explicit PlainObjectBase(const std::initializer_list<std::initializer_list<Scalar>>& list);
如果您总是想使用 3D 向量,那么(更简单的)替代方法是使用 Eigen 的 3D 构造函数和聚合初始化:
CustomVector3(double x,double y,double z) : Vector3(x,y,z) {}
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