Part VI contains programming patterns that require an understanding of objects and references, and parameter passing. Specifically, this part of the book contains the following programming patterns:
Chained Mutators. A solution to the problem of invoking multiple different methods on the same object, one right after another.
Outbound Parameters. A solution to the problem of needing to return multiple pieces of information from a single method.
Missing Values. A solution to the problem of distinguishing missing values from actual values so that they can be handled differently when performing calculations of various kinds.
Checklists. A solution to the problem of checking to see whether a specific set of criteria (identified at run-time) have been satisfied.
The chained mutators pattern involves the return of a reference, while the outbound parameters pattern involves passing references. The missing values pattern takes advantage of the “special” reference
null. Finally, the checklists pattern is a generalization of the bit flags pattern that allows for the set of criteria to be created dynamically (i.e., at run-time).