Search in a vector of structs - c++

Question

I have a vector full with structs look like this
struct person_t
{
string name;
string id;
struct location_t location;
};
vector <person_t> myvector;
and i have read in the items in myvector
but now i need to know how to search for specific item in vector and count how many of that item it is in the vector.

Answer 1

unsigned int count = std::count_if( myvector.begin(), myvector.begin(),
[]( const person_t & p ) { return p.name == "Bill Gates"; }
);
or without c++11
struct EqualByName {
EqualByName( const std::string & name ) : m_name( name ) {}
bool operator()( const person_t & p ) const { return p.name == m_name; }
private:
std::string m_name;
};
unsigned int count = std::count_if( myvector.begin(), myvector.begin(),
EqualByName( "Bill Gates" )
);
or ugly looking but for all occasions ))
template< class T, class FieldType, FieldType T::*FieldPtr >
struct EqualBy
{
EqualBy( const FieldType & value ) : m_fieldValue( value ) {}
bool operator()( const T & r ) const {
return m_fieldValue == r.*FieldPtr;
}
bool operator()( const T * p ) const {
return m_fieldValue == p->*FieldPtr;
}
private:
const FieldType m_fieldValue;
};
// usage:
typedef EqualBy< person_t, std::string, & person_t::name > EqualByName;
typedef EqualBy< person_t, std::string, & person_t::id > EqualById;
unsigned int namesCount = std::count_if( myvector.begin(), myvector.end(),
EqualByName( "Bill Gates" )
);
unsigned int idsCount = std::count_if( myvector.begin(), myvector.end(),
EqualById( "123456" )
);