Good software structure is essential for system extension and maintenance. Software development is a chaotic activity, therefore the implemented structure of systems tends to stray from the planned structure as determined by architecture, analysis, and design.
Software refactoring is an effective approach for improving software structure.
The resulting structure does not have to resemble the original planned structure.
The structure changes because programmers learn constraints and approaches that alter the context of the coded solutions. When used properly, refactoring is a natural activity in the programming process.
For example, the solution for the Spaghetti Code AntiPattern defines a software development process that incorporates refactoring. Refactoring is strongly recommended prior to performance optimization. Optimizations often involve compromises to program structure. Ideally, optimizations affect only small portions of a program. Prior refactoring helps partition optimized code from the majority of the software.
Development AntiPatterns utilize various formal and informal refactoring approaches. The following summaries provide an overview of the Development AntiPatterns found in this chapter and focus on the development AntiPattern problem. Included are descriptions of both development and mini-AntiPatterns. The refactored solutions appear in the appropriate AntiPattern templates that follow the summaries.
The Blob
Procedural-style design leads to one object with a lion’s share of the responsibilities, while most other objects only hold data or execute simple processes. The solution includes refactoring the design to distribute responsibilities more uniformly and isolating the effect of changes.
Continuous Obsolescence
Technology is changing so rapidly that developers often have trouble keeping up with current versions of software and finding combinations of product releases that work together.
Given that every commercial product line evolves through new releases, the situation is becoming more difficult for developers to cope with. Finding compatible releases of products that successfully interoperate is even harder.
Lava Flow
Dead code and forgotten design information is frozen in an ever-changing design. This is analogous to a Lava Flow with hardening globules of rocky material. The refactored solution includes a configuration management process that eliminates dead code and evolves or refactors design toward increasing quality.
Ambiguous Viewpoint
Object-oriented analysis and design (OOA & D) models are often presented without clarifying the viewpoint represented by the model. By default, OOA & D models denote an implementation viewpoint that is potentially the least useful. Mixed viewpoints don’t allow the fundamental separation of interfaces from implementation details, which is one of the primary benefits of the object-oriented paradigm.
Functional Decomposition
This AntiPattern is the output of experienced, nonobject-oriented developers who design and implement an application in an object-oriented language. The resulting code resembles a structural language (Pascal, FORTRAN) in class structure. It can be incredibly complex as smart procedural developers devise very “clever” ways to replicate their time-tested methods in an object-oriented architecture.
Poltergeists
Poltergeists are classes with very limited roles and effective life cycles. They often start processes for other objects.
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