Using a follow-on survey to investigate why use of the Visitor, Singleton & Facade patterns is controversial

Context: A previous study has shown that software developers who are experienced with using design patterns hold some conflicting opinions about three of the more popular design patterns: Facade, Singleton and Visitor. Aim: To identify the characteristics of these three patterns that have caused them to generate such differing views. Method: We employed a qualitative follow-on survey of those developers who had taken part in the earlier survey about design patterns. Results: We received 46 usable responses from a possible total of 188, with nearly 85% of respondents having six or more years of experience with design patterns. Of these, 27 also provided comments and descriptions of experiences about the patterns, which we categorised. Conclusions: All three patterns can easily be misused and in each case, the consequences of misuse are regarded as being particularly significant.