multimap::value_type

表示映射中的元素存储的对象的类型的类型。

typedef pair<const Key, Type> value_type;

备注

使用非常数迭代器，或引用，因为一关联容器中的密钥不能更改value_type 声明为 pair*<const key_typemapped_type>pair* <，而不是key_type，mapped_type>。

示例

// multimap_value_type.cpp
// compile with: /EHsc
#include <map>
#include <iostream>

int main( )
{
   using namespace std;
   typedef pair <const int, int> cInt2Int;
   multimap <int, int> m1;
   multimap <int, int> :: key_type key1;
   multimap <int, int> :: mapped_type mapped1;
   multimap <int, int> :: value_type value1;
   multimap <int, int> :: iterator pIter;
   
   // value_type can be used to pass the correct type
   // explicitely to avoid implicit type conversion
   m1.insert ( multimap <int, int> :: value_type ( 1, 10 ) );

   // Compare another way to insert objects into a hash_multimap
   m1.insert ( cInt2Int ( 2, 20 ) );

   // Initializing key1 and mapped1
   key1 = ( m1.begin( ) -> first );
   mapped1 = ( m1.begin( ) -> second );

   cout << "The key of first element in the multimap is "
        << key1 << "." << endl;

   cout << "The data value of first element in the multimap is "
        << mapped1 << "." << endl;

   // The following line would cause an error because
   // the value_type is not assignable
   // value1 = cInt2Int ( 4, 40 );

   cout  << "The keys of the mapped elements are:";
   for ( pIter = m1.begin( ) ; pIter != m1.end( ) ; pIter++ )
      cout << " " << pIter -> first;
   cout << "." << endl;

   cout  << "The values of the mapped elements are:";
   for ( pIter = m1.begin( ) ; pIter != m1.end( ) ; pIter++ )
      cout << " " << pIter -> second;
   cout << "." << endl;
}

要求

标头: <map>

命名空间: std

请参见

参考

multimap 类

标准模板库