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{{Refimprove|date=July 2007}}
In [[computer programming]], a '''poltergeist''' (or '''gypsy wagon''') is a short-lived, typically [[State (computer science)|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 [[Vardo (Romani wagon)|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
A poltergeist can often be identified by its name; they are often called "manager_", "controller_", "supervisor", "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 [[Software design pattern|pattern]] such as [[model–view–controller]], or tier-separating patterns such as [[business-delegate]].
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