template< class KEY, class ARG_KEY, class VALUE, class ARG_VALUE >class CMap : public CObject
- Class of the object used as the key to the map.
- Data type used for KEY arguments; usually a reference to KEY.
- Class of the object stored in the map.
- Data type used for VALUE arguments; usually a reference to VALUE.
CMap is a dictionary collection class that maps unique keys to values. Once you have inserted a key-value pair (element) into the map, you can efficiently retrieve or delete the pair using the key to access it. You can also iterate over all the elements in the map.
A variable of type POSITION is used for alternate access to entries. You can use a POSITION to "remember" an entry and to iterate through the map. You might think that this iteration is sequential by key value; it is not. The sequence of retrieved elements is indeterminate.
Certain member functions of this class call global helper functions that must be customized for most uses of the CMap class. See Collection Class Helpers in the Macros and Globals section of the MFC Reference.
CMap incorporates the IMPLEMENT_SERIAL macro to support serialization and dumping of its elements. Each element is serialized in turn if a map is stored to an archive, either with the overloaded insertion (<<) operator or with the Serialize member function.
If you need a diagnostic dump of the individual elements in the map (the keys and the values), you must set the depth of the dump context to 1 or greater.
When a CMap object is deleted, or when its elements are removed, the keys and values both are removed.
Map class derivation is similar to list derivation. See the article Collections for an illustration of the derivation of a special-purpose list class.