c++ - 如何在 multi_index_container 中添加指定的有序唯一索引

Question

我正在使用 boost:multi_index_container。以下是代码

#include <string>
#include <boost/multi_index_container.hpp>
#include "boost/multi_index/global_fun.hpp"
#include "boost/multi_index/hashed_index.hpp"
#include <boost/multi_index/sequenced_index.hpp>
#include "boost/multi_index/mem_fun.hpp"
#include "boost/multi_index/member.hpp"
#include "boost/multi_index/ordered_index.hpp"
#include "boost/multi_index/indexed_by.hpp"

using namespace std;

class uri
{
public:
    string str;
    uri(string s) :str(s)
    {
    }
    string getUri(){ return str; }

};


struct UriWithBase
{
    UriWithBase(uri u1, uri u2) :link(u1), baseLink(u2){}
    uri link;
    uri baseLink;
};



int main()
{
    typedef boost::multi_index::multi_index_container <
        UriWithBase*,
        boost::multi_index::indexed_by <
        boost::multi_index::sequenced < >
        >
    > UriMultiIndex;

    UriMultiIndex m_uris;

    uri urib1("www.google.com");
    uri uri1("www.news.google.com");

    UriWithBase *ubptr = new UriWithBase(uri1, urib1);

    m_uris.push_back(ubptr);
    return 0;
}

现在我想添加在 multi_index_container 中指定的有序唯一索引。该索引用于容器中元素的唯一顺序，取决于“UriWithBase”类的第一个元素，即 uri 链接。我尝试关注但没有成功。boost::multi_index::ordered_unique<

    boost::multi_index::tag<uris_by_uri>,
BOOST_MULTI_INDEX_CONST_MEM_FUN(UriWithBasePtr, const uri&, (*(UriWithBasePtr)).link)>

Answer 1

class uri
{
public:
    string str;
    uri(string s) :str(s)
    {
    }

    // note we made this const
    string getUri() const { return str; }
};

inline bool operator<(const uri& x,const uri& y)
{
  return x.getUri()<y.getUri();
}

...

typedef boost::multi_index::multi_index_container <
    UriWithBase*,
    boost::multi_index::indexed_by <
    boost::multi_index::sequenced < >,
    boost::multi_index::ordered_unique<
        boost::multi_index::tag<uris_by_uri_and_crawl_state>,
        boost::multi_index::member<UriWithBase,uri,&UriWithBase::link>
    >
    >
> UriMultiIndex;