c++ - boost multi_index修改成员并保留序列

Question

我正在使用 boost::multi_index 容器。基本上它包括一些数据加上数据集信息是否完整的信息(当一个项目被添加到容器时，信息还没有完成)。容器已排序，因为我必须知道订单项已添加到容器中。

#include <boost/multi_index_container.hpp>    
#include <boost/multi_index/hashed_index.hpp>    
#include <boost/multi_index/ordered_index.hpp>    
#include <boost/multi_index/member.hpp>    
#include <boost/multi_index/composite_key.hpp>    
#include <boost/multi_index/sequenced_index.hpp>    
#include <boost/multi_index/key_extractors.hpp>    


struct indexed_struct    
{    
    unsigned int identifier;    
    unsigned int iterationFinished;    

    indexed_struct():    
        identifier(0), iterationFinished(0){}

    indexed_struct(unsigned int identifier, unsigned int iterationFinished):    
        identifier(identifier), iterationFinished(iterationFinished){}



    friend std::ostream& operator<<(std::ostream& os,const indexed_struct& c)    
    {    
        os<<c.identifier<<std::endl;    
        return os;    
    }
};

struct identifierTag {};    
struct finishedTag {};


typedef boost::multi_index::multi_index_container<    
    indexed_struct,    
        boost::multi_index::indexed_by<boost::multi_index::sequenced<>,    
            boost::multi_index::ordered_unique<boost::multi_index::tag<identifierTag>,    
            BOOST_MULTI_INDEX_MEMBER(indexed_struct, unsigned int, identifier)    
        >,    
        boost::multi_index::ordered_non_unique<boost::multi_index::tag<finishedTag>,    
            BOOST_MULTI_INDEX_MEMBER(indexed_struct, unsigned int, iterationFinished)    
        >    
    >    
> cmm_iteration_table;



void setFinished(cmm_iteration_table& table, unsigned int iteration)    
{    
    cmm_iteration_table::index<identifierTag>::type::iterator it;    
    it = table.get<identifierTag>().find(iteration);    
    indexed_struct mod(*it);    
    mod.iterationFinished = 1;    
    table.get<identifierTag>().replace(it, mod);

}


void main()    
{    
    cmm_iteration_table table;

    //add some items with iterationFinished set to 0    
    table.push_back(indexed_struct(30,0));    
    table.push_back(indexed_struct(20,0));    
    table.push_back(indexed_struct(40,0)); 

    //now set iterationFinished to 1 in a random order
    setFinished(table, 30);    
    setFinished(table, 40);    
    setFinished(table, 20);

    //try to get iterator for iterationFinished == 1 and sequenced
    //30-20-40 as added

    std::copy(table.get<finishedTag>().equal_range(1).first, table.get<finishedTag>().equal_range(1).second, std::ostream_iterator<indexed_struct>(std::cout)); //outputs 20,40,30 but 30, 20, 40 is intended

    std::copy(table.begin(), table.end(), std::ostream_iterator<indexed_struct>(std::cout)); //outputs 30,20,40, but would also output items where iterationFinished == 0

}

我想获得一个迭代器对，迭代 iterationFinished 设置为 1 的已排序项。

第一个 std::copy 带有指向 iterationFinished 标志的索引，但顺序不正确(意思是我希望顺序作为被插入容器的项目)

第二个 std::copy 给出了正确的顺序，但也会打印 iterationFinished == 0 的项目。

有什么提示吗？

Answer 1

尝试使用 boost::filter_iterator

像这样:

struct is_finished 
{
    bool operator()(indexed_struct const& x) { return x.iterationFinished; }
};

typedef cmm_iteration_table::index<identifierTag>::type::iterator iterator_type;

iterator_type it, ite;    
it = table.get<identifierTag>().begin();
ite = table.get<identifierTag>().end();

typedef boost::filter_iterator<is_finished, iterator_type> filter_iter_t;
filter_iter_t f_it(is_finished(), it, ite), f_ite(is_finished(), ite, ite);

std::copy(f_it, f_ite, std::ostream_iterator<indexed_struct>(std::cout));