从std :: vector中删除项目 [英] Removing an item from an std:: vector

问题描述

在下面的第一个代码片段中，我试图从一个成员函数中的向量中删除一个元素，基于一个静态条件函数馈入std :: remove函数。然后，我得到大量的模板错误显示在第二个片段。

$ b

SNIPPET 1（CODE）

  void removeVipAddress（std :: string& uuid）
 {
 struct RemoveCond 
 {
 static bool condition（const VipAddressEntity& o）
 {
 return o.getUUID（）== uuid; 
} 
}; 
 
 std :: vector< VipAddressEntity> :: iterator last = 
 std :: remove（
 mVipAddressList.begin（），
 mVipAddressList.end b $ b RemoveCond :: condition）; 
 
 mVipAddressList.erase（last，mVipAddressList.end（））; 
 
} 
  

SNIPPET 2 （COMPILATION OUTPUT ）

  /usr/include/c++/4.7/bits/random.h:4845:5：note：template< class _IntType> ; bool std :: operator ==（const std :: discrete_distribution< _IntType>& const std :: discrete_distribution< _IntType>&）
 /usr/include/c++/4.7/bits/random.h:4845 ：5：注意：模板参数扣除/替换失败：
在/usr/include/c++/4.7/algorithm:63:0中包含的文件中，
来自Entity.hpp：12：
 /usr/include/c++/4.7/bits/stl_algo.h:174:4：注意：'ECLBCP :: VipAddressEntity'不是从'const std :: discrete_distribution< _IntType>'
派生的在从/ usr / include / c ++ / 4.7 / random：50：0，
来自/usr/include/c++/4.7/bits/stl_algo.h:67，
来自/usr/include/c++/4.7/算法：63，
来自Entity.hpp：12：
 /usr/include/c++/4.7/bits/random.h:4613:5：note：template< class _RealType> bool std :: operator ==（const std :: extreme_value_distribution< _RealType>& const std :: extreme_value_distribution< _RealType>&）
 /usr/include/c++/4.7/bits/random.h:4613 ：5：注意：模板参数扣除/替换失败：
在/usr/include/c++/4.7/algorithm:63:0中包含的文件中，
来自Entity.hpp：12：
 /usr/include/c++/4.7/bits/stl_algo.h:174:4：注意：'ECLBCP :: VipAddressEntity'不是从'const std :: extreme_value_distribution< _RealType>'派生的
  std :: remove_if（）  / code>，而非 std :: remove（）。
 
 
 
  std :: remove_if（）接受一个谓词作为第三个参数，并删除满足该谓词的元素。
 
 
 
  std： ：remove（）将值作为第三个参数，并删除等于该值的元素。
 
 
 
  
 
 
 
要使这项工作，您还必须将您的 RemoveCond 定义变成谓词对象，因为它需要州。像这样：
  void removeVipAddress（std :: string& uuid）
 {
 struct RemoveCond： public std :: unary_function< VipAddressEntity，bool> 
 {
 std :: string uuid; 
 
 RemoveCond（const std :: string& uuid）：uuid（uuid）{} 
 
 bool operator（）（const VipAddressEntity& o）
 { 
 return o.getUUID（）== uuid; 
} 
}; 
 
 std :: vector< VipAddressEntity> :: iterator last = 
 std :: remove（
 mVipAddressList.begin（），
 mVipAddressList.end（），
 RemoveCond（uuid））; 
 
 mVipAddressList.erase（last，mVipAddressList.end（））; 
 
} 
  
 
In the 1st code snippet below, I am trying to remove an element from a vector within a member function based on a static condition function fed into std::remove function. Then I am getting lots of template errors shown in the 2nd snippet. Can you please tell me what I am missing?

SNIPPET 1 (CODE)
void removeVipAddress(std::string &uuid)
{
          struct RemoveCond
          {
            static bool condition(const VipAddressEntity & o)
            {
              return o.getUUID() == uuid;
            }
          };

          std::vector<VipAddressEntity>::iterator last =
            std::remove(
                    mVipAddressList.begin(),
                    mVipAddressList.end(),
                    RemoveCond::condition);

          mVipAddressList.erase(last, mVipAddressList.end());

}
SNIPPET 2 (COMPILATION OUTPUT)
 /usr/include/c++/4.7/bits/random.h:4845:5: note: template<class _IntType> bool      std::operator==(const std::discrete_distribution<_IntType>&, const   std::discrete_distribution<_IntType>&)
 /usr/include/c++/4.7/bits/random.h:4845:5: note:   template argument deduction/substitution failed:
 In file included from /usr/include/c++/4.7/algorithm:63:0,
             from Entity.hpp:12:
 /usr/include/c++/4.7/bits/stl_algo.h:174:4: note:   ‘ECLBCP::VipAddressEntity’ is not  derived from ‘const std::discrete_distribution<_IntType>’
 In file included from /usr/include/c++/4.7/random:50:0,
               from /usr/include/c++/4.7/bits/stl_algo.h:67,
               from /usr/include/c++/4.7/algorithm:63,
               from Entity.hpp:12:
 /usr/include/c++/4.7/bits/random.h:4613:5: note: template<class _RealType> bool  std::operator==(const std::extreme_value_distribution<_RealType>&, const  std::extreme_value_distribution<_RealType>&)
 /usr/include/c++/4.7/bits/random.h:4613:5: note:   template argument deduction/substitution failed:
 In file included from /usr/include/c++/4.7/algorithm:63:0,
             from Entity.hpp:12:
 /usr/include/c++/4.7/bits/stl_algo.h:174:4: note:   ‘ECLBCP::VipAddressEntity’ is not  derived from ‘const std::extreme_value_distribution<_RealType>’

解决方案
I guess you're looking for std::remove_if(), not std::remove().

std::remove_if() accepts a predicate as it third argument, and removes elements satisfying that predicate.

std::remove() takes a value as the third argument, and removes elements equal to the value.

EDIT

To make this work, you will also have to turn your RemoveCond definition into a predicate object, because it needs state. Like this:
void removeVipAddress(std::string &uuid)
{
      struct RemoveCond : public std::unary_function<VipAddressEntity, bool>
      {
        std::string uuid;

        RemoveCond(const std::string &uuid) : uuid(uuid) {}

        bool operator() (const VipAddressEntity & o)
        {
          return o.getUUID() == uuid;
        }
      };

      std::vector<VipAddressEntity>::iterator last =
        std::remove(
                mVipAddressList.begin(),
                mVipAddressList.end(),
                RemoveCond(uuid));

      mVipAddressList.erase(last, mVipAddressList.end());

}


                        
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