Incomplete Library Class

Signs and Symptoms

Sooner or later, libraries stop meeting user needs. The only solution to the problem—changing the library—is often impossible since the library is read-only.

Reasons for the Problem

The author of the library hasn’t provided the features you need or has refused to implement them.

Treatment

• To introduce a few methods to a library class, use Introduce Foreign Method.

• For big changes in a class library, use Introduce Local Extension.

Payoff

• Reduces code duplication (instead of creating your own library from scratch, you can still piggy-back off an existing one).

When to Ignore

• Extending a library can generate additional work if the changes to the library involve changes in code.