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电梯直达

1楼 [收藏(0)] [报告]

发表于 2009-05-27 10:09 |只看该作者 |倒序浏览

比如一个列表中是一个类，我想实现在该列表中，是否有某个对象中成员是否含某个值：但以下代码在用find_if的时候编译不过
高手过来说说，该怎么弄，看stl中的find_if实现，就是:

template <class InputIterator, class Predicate>
InputIterator find_if(InputIterator first, InputIterator last,
                  Predicate pred) {
  while (first != last && !pred(*first)) ++first;
  return first;
}

#include <string>
#include <vector>
using namespace std;
class CTest
{
private:
    int ii;
    string str;
public:
    CTest() {};
    CTest(int i):ii(i){ };
    CTest(string &s) : str(s)
        {
        }
    CTest(int i, string &s) : ii(i), str(s) {}
    int get_ii(){
        return ii;
    }
    string &get_str()
        {
            return str;
        }
};

typedef int (*pf)() ;
template<class T, class itor>
class cmp
{
public:
    cmp(T &v, pf f) : m_value(v), m_f(f) {}
    bool operator ()(itor it)
        {
            return (m_value == it->m_f());
        }
private:
    pf m_f;
    T m_value;
};

int main(int argc, char *argv[])
{
    vector<CTest> vTest;
    for (int i=0; i<10; ++i)
    {
        char sz[100];
        sprintf(sz, "%d", i+100);
        string s(sz);
        CTest c(i, s);
        vTest.push_back(c);
    }

    vector<CTest>::iterator it, end=vTest.end();
    for (it=vTest.begin(); it!=end; ++it)
    {
        printf("ii=%d\tstr=%s\n", it->get_ii(), it->get_str().c_str());
    }

    it = find_if(vTest.begin(), end, cmp(8, CTest::get_ii));
    if (it==end)
        printf("not found\n");
    else
    {
        printf("found\n");
        printf("ii=%d\tstr=%s\n", it->get_ii(), it->get_str().c_str());
    }
    return 0;
}

[ 本帖最后由 freebarque 于 2009-5-27 10:14 编辑 ]

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bruceteen

腰缠万贯

论坛徽章:: 14

2楼 [报告]

发表于 2009-05-27 15:20 |只看该作者

#include <string>

class CTest
{
public:
CTest( int i=0 ) : i_(i)
{
}
CTest( const char* s ) : i_(0), str_(s)
{
}
CTest( int i, const char* s ) : i_(i), str_(s)
{
}
int get_i() const
{
return i_;
}
const std::string& get_str() const
{
return str_;
}
private:
int i_;
std::string str_;
};

struct cmp
{
cmp( int (CTest::*pmf)() const, int val ) : pmf_(pmf), val_(val)
{
}
bool operator()( const CTest& t ) const
{
return (t.*pmf_)() == val_;
}
private:
int (CTest::*pmf_)() const;
int val_;
};

#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int main(int argc, char *argv[])
{
vector<CTest> vTest;
for( int i=0; i<10; ++i )
{
char sz[100];
sprintf(sz, "%d", i+100);
vTest.push_back( CTest(i,sz) );
}

for( vector<CTest>::iterator it=vTest.begin(); it!=vTest.end(); ++it )
{
printf( "i=%d\tstr=%s\n", it->get_i(), it->get_str().c_str() );
}

cout << "---------------" << endl;

vector<CTest>::iterator it = find_if( vTest.begin(), vTest.end(), cmp(&CTest::get_i,

);
if( it == vTest.end() )
printf( "%s", "not found\n" );
else
printf( "i=%d\tstr=%s\n", it->get_i(), it->get_str().c_str() );

return 0;
}

[ 本帖最后由 bruceteen 于 2009-5-27 15:21 编辑 ]

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bruceteen

腰缠万贯

论坛徽章:: 14

3楼 [报告]

发表于 2009-05-27 15:29 |只看该作者

如果希望cmp是个模板类，且完全隐式推导的话：

#include <string>

class CTest
{
public:
CTest( int i=0 ) : i_(i)
{
}
CTest( const char* s ) : i_(0), str_(s)
{
}
CTest( int i, const char* s ) : i_(i), str_(s)
{
}
int get_i() const
{
return i_;
}
const std::string& get_str() const
{
return str_;
}
private:
int i_;
std::string str_;
};

template<class T,typename V>
struct cmp
{
cmp( V (T::*pmf)() const, V val ) : pmf_(pmf), val_(val)
{
}
bool operator()( const T& t ) const
{
return (t.*pmf_)() == val_;
}
private:
V (CTest::*pmf_)() const;
V val_;
};
template<class T,typename V>
cmp<T,V> makecmp( V (T::*pmf)() const, V val )
{
return cmp<T,V>( pmf, val );
}

#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int main(int argc, char *argv[])
{
vector<CTest> vTest;
for( int i=0; i<10; ++i )
{
char sz[100];
sprintf(sz, "%d", i+100);
vTest.push_back( CTest(i,sz) );
}

for( vector<CTest>::iterator it=vTest.begin(); it!=vTest.end(); ++it )
{
printf( "i=%d\tstr=%s\n", it->get_i(), it->get_str().c_str() );
}

cout << "---------------" << endl;

vector<CTest>::iterator it = find_if( vTest.begin(), vTest.end(), makecmp(&CTest::get_i,

);
if( it == vTest.end() )
printf( "%s", "not found\n" );
else
printf( "i=%d\tstr=%s\n", it->get_i(), it->get_str().c_str() );

return 0;
}