为了使自定义类（继承自STL容器（如std::vector或std::map））与boost::assign list_of()或map_list_of()初始化函数一起工作，我该怎么做？
我想轻松地用值列表初始化容器。C ++ 11引入了初始值设定项列表，但是我被C ++ 03所困扰，所以我不能使用C ++ 11初始值设定项列表。
作为一种解决方法，我发现了boost：assign库，它提供了诸如list_of（）和map_list_of（）之类的功能。这对于像std :: vector和std :: map这样的STL容器来说效果很好。但是，如果我通过扩展std :: vector创建自己的容器，则会出现编译错误。
这是一个小例子
#include "boost/assign/list_of.hpp"
using namespace boost::assign;
#include <vector>
struct SpecialVector : public std::vector<int>{
foo(){/* adds functionality */}
};
int main(){
std::vector<int> v = list_of(1)(2)(3); // list_of() works well for STL containers
// The following works but requires adding items one-by-one with push_back
SpecialVector u;
u.push_back(1);
u.push_back(2);
u.push_back(3);
// The following fails when attempting to compile
SpecialVector u2 = list_of(1)(2)(3);
}
尝试编译该示例会给我以下错误：
In file included from assign_inherited.cpp:1:0:
../../../lib/boost/assign/list_of.hpp: In instantiation of 'Container boost::assign_detail::converter<DerivedTAssign, Iterator>::convert(const Container*, boost::assign_detail::default_type_tag) const [with Container = SpecialVector; DerivedTAssign = boost::assign_detail::generic_list<int>; Iterator = std::_Deque_iterator<int, int&, int*>]':
../../../lib/boost/assign/list_of.hpp:142:38: required from 'Container boost::assign_detail::converter<DerivedTAssign, Iterator>::convert_to_container() const [with Container = SpecialVector; DerivedTAssign = boost::assign_detail::generic_list<int>; Iterator = std::_Deque_iterator<int, int&, int*>]'
../../../lib/boost/assign/list_of.hpp:436:81: required from 'boost::assign_detail::generic_list<T>::operator Container() const [with Container = SpecialVector; T = int]'
assign_inherited.cpp:19:39: required from here
../../../lib/boost/assign/list_of.hpp:163:20: error: no matching function for call to 'SpecialVector::SpecialVector(boost::assign_detail::converter<boost::assign_detail::generic_list<int>, std::_Deque_iterator<int, int&, int*> >::iterator, boost::assign_detail::converter<boost::assign_detail::generic_list<int>, std::_Deque_iterator<int, int&, int*> >::iterator)'
return Container( begin(), end() );
^~~~~~~~~~~~~~~~~~~~~~~~~~~
assign_inherited.cpp:5:8: note: candidate: SpecialVector::SpecialVector()
struct SpecialVector : public std::vector<int>{
^~~~~~~~~~~~~
assign_inherited.cpp:5:8: note: candidate expects 0 arguments, 2 provided
assign_inherited.cpp:5:8: note: candidate: SpecialVector::SpecialVector(const SpecialVector&)
assign_inherited.cpp:5:8: note: candidate expects 1 argument, 2 provided
我已经检查了boost :: assign库的文档。我找到了“扩展库”部分，但是，如果我对它的理解正确，那么本部分将把自定义类作为列表中的项添加，而不是为自定义类生成初始化器。还是我理解错了？
就像您说的那样，您需要允许从基本类型进行构造：
#include "boost/assign/list_of.hpp"
using namespace boost::assign;
#include <vector>
struct SpecialVector : std::vector<int>{
typedef std::vector<int> base;
void foo(){/* adds functionality */}
SpecialVector() : base() {}
template <typename T> explicit SpecialVector(T const& t) : base(t) {}
template <typename T, typename U> SpecialVector(T const& t, U const& u) : base(t, u) {}
template <typename T, typename U, typename V> SpecialVector(T const& t, U const& u, V const& v) : base(t, u, v) {}
};
int main(){
std::vector<int> v = list_of(1)(2)(3); // list_of() works well for STL containers
// The following works but requires adding items one-by-one with push_back
SpecialVector u;
u.push_back(1);
u.push_back(2);
u.push_back(3);
// The following fails when attempting to compile
SpecialVector u2 = list_of(1)(2)(3);
}
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