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In computer programming, a poltergeist (or gypsy wagon) is a short-lived, typically stateless object used to perform initialization or to invoke methods in another, more permanent class. It is considered an anti-pattern. The original definition is by Michael Akroyd 1996 - Object World West Conference: :"As a gypsy wagon or a poltergeist appears and disappears mysteriously, so does this short lived object. As a consequence the code is more difficult to maintain and there is unnecessary resource waste. The typical cause for this antipattern is poor object design." A poltergeist can often be identified by its name; they are often called "manager_", "controller_", "start_process", etc. Sometimes, poltergeist classes are created because the programmer anticipated the need for a more complex architecture. For example, a poltergeist arises if the same method acts as both the ''client'' and ''invoker'' in a Command pattern, and the programmer anticipates separating the two phases. However, this more complex architecture may actually never materialize. Poltergeists should not be confused with long-lived, state-bearing objects of a pattern such as Model-view-controller, or tier-separating patterns such as Business-Delegate. To remove a poltergeist, delete the class and insert its functionality in the invoked class, possibly by inheritance or as a mixin. ==See also== *Anti-pattern *YAGNI principle 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Poltergeist (computer programming)」の詳細全文を読む スポンサード リンク
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