Data Structures and Algorithms
with Object-Oriented Design Patterns in C++ 
An association is an ordered pair of objects. The first element of the pair is called the key ; the second element is the value associated with the given key.
Associations are useful for storing information in a database for later retrieval. E.g., a database can be viewed as a collection of key-and-value pairs. The information associated with a given key is retrieved from the database by searching the database for an the ordered pair in which the key matches the given key.
An association is like a container in that it contains two objects--the key and the value. On the other hand, an association is fundamentally different from a container since the contained objects are treated very differently. Normally, the objects in a container are not distinguished one from another. In an association, the two contained objects are distinct--one of them is the key and the other is a value associated with the key.
Program 
gives the declaration
of the concrete object class Association.
The declaration of the Association class
is like that of Container class
in that both of them are derived from the same set of base classes--Object and Ownership.
Program: Association Class Definition
An association has two member variables, key and value, both of which are of type pointer to Object. Since pointers are used, the Association class implements indirect containment.
Copyright © 1997 by Bruno R. Preiss, P.Eng. All rights reserved.