我正在尝试创建动态属性映射。为此,我创建了单独的属性映射,Dynamic_attribute,然后创建了一个容器,它是std :: unordered_map来存储它们。我写道,下面是代码。但是在使用g ++选项-std = c ++ 0x进行编译时会产生一个非常奇怪的错误。
#include <iostream>
#include <vector>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <string>
#include <typeinfo>
#include <cstdlib>
#include <cstring>
#include <boost/property_map/property_map.hpp>
#include <boost/property_map/dynamic_property_map.hpp>
class Dynamic_attribute_base{
public:
Dynamic_attribute_base(const std::string& name) : name_(name){}
/// Destructor
virtual ~Dynamic_attribute_base(){}
/// Destroy the object
virtual void destroy() = 0;
protected:
std::string name_;
};
/// @models
/// - LValuePropertyMap
/// - std:unordered_map
template<typename Key, typename Value>
class Dynamic_attribute
: public Dynamic_attribute_base{
public:
typedef Key key_type;
typedef Value value_type;
typedef std::unordered_map<key_type, value_type> map_type;
typedef typename map_type::reference referencnce;
typedef typename map_type::const_reference const_reference;
/// Constructor
Dynamic_attribute(const std::string& name):
Dynamic_attribute_base(name) {}
public: // virtual interface of Dynamic_attribute_base
virtual void destroy(){
data_.clear();
this->~Dynamic_attribute();
}
public:
/// Return the value corresponding to key k.
/// if key doesn't exists unexpected value is returned.
value_type get(key_type& k){
assert(!data_.empty());
if (data_.find(k) != data_.end()){
return data_[k];
}
else{
std::cout<<"Key not found"<< std::endl;
return NULL;
}
}
/// Set the property corresponding to particular Key K
/// to value V.
void set(key_type& k, value_type& v){
data_[k] = v;
}
/// Remove a key from the map.
void remove(key_type& k){
data_.erase(k);
}
protected:
map_type data_;
};
std::unordered_map< std::pair<std::string,unsigned int> , Dynamic_attribute_base*> d_attribute_container;
template<typename T>
void add_dynamic_attribute(unsigned int admin, std::string name){
if (d_attribute_container.find(make_pair(name,admin)) != d_attribute_container.end()){
std::cout<<"Error. Key already exists.";
return;
}
Dynamic_attribute<int, T> *d_attr = new Dynamic_attribute<int, T>(name);
d_attribute_container[make_pair(name,admin)] = d_attr;
}
template<typename T>
T get_dart_attribute(int handle, unsigned int admin, std::string name){
if (d_attribute_container.find(make_pair(name,admin)) == d_attribute_container.end()){
std::cout<<"Error. Key doesn't exists.";
return;
}
return dynamic_cast<Dynamic_attribute<int,T>*>(d_attribute_container[make_pair(name,admin)])->get(handle);
}
int main()
{
add_dynamic_attribute<std::string>(1,"first");
add_dynamic_attribute<double>(2,"second");
add_dynamic_attribute<double>(2,"second");
return 0;
}
我收到的错误讯息
/tmp/ccLK64Ja.o:在函数std::__detail::_Hash_code_base<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int>, std::pair<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> const, Dynamic_attribute_base*>, std::_Select1st<std::pair<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> const, Dynamic_attribute_base*> >, std::equal_to<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> >, std::hash<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, false>::_M_hash_code(std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> const&) const':
main.cpp:(.text._ZNKSt8__detail15_Hash_code_baseISt4pairISsjES1_IKS2_P22Dynamic_attribute_baseESt10_Select1stIS6_ESt8equal_toIS2_ESt4hashIS2_ENS_18_Mod_range_hashingENS_20_Default_ranged_hashELb0EE12_M_hash_codeERS3_[std::__detail::_Hash_code_base<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int>, std::pair<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> const, Dynamic_attribute_base*>, std::_Select1st<std::pair<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> const, Dynamic_attribute_base*> >, std::equal_to<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> >, std::hash<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, false>::_M_hash_code(std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned int> const&) const]+0x37): undefined reference to
std :: hash,std :: allocator&gt;中,unsigned int&gt; &gt; :: operator()(std :: pair,std :: allocator&gt;,unsigned int&gt;)const&#39;
有什么想法吗?
答案 0 :(得分:1)
你需要为你的对专门化std::hash
,或者为它提供一个哈希模板参数。