An "Association" associates a key to a value.

Here we see an association that associates the key "K20299820" (an id) with a value that is a "Student" object.

Here we show a set of associations, each associating a certain key with a specific value.

• For example, the key "PI" (math symbol) is associated with the number 3.1416.
• And the key "WA" (state abbrev) is associated with the full name "Washington"

Note association values are flexible. We could associate "WA" with a string (like we do here), but we could also associate it with a full-fledged "State" object.

Let us try to define an Association so we can code it:

• We have a key
• We have a value

By having these two properties we "tie together" (or associate) the key with the value.

Class: Association

Instance Variables:

• key
• value

e.g.:

• key = "WA"
• value = "Washington"

Associations are used as part of composite objects.

A "Map" (or dictionary) is a common example.

We may have a small map (e.g. like a map of states keyed by state abbrev as we show here), or a larger one like a map of all employees of a corporation keyed by employee id.