Registry Design Pattern keeping track of objects

Registry Motivation & Provenance non-canonical (not out of Gamma et al) design pattern described by Martin Fowler in "Patterns of Enterprise Application Architecture" well-known object that other objects use to find common objects and services

Registry Implementation details registry is usually a global object may be implemented as singleton objects to be looked up register with the registry object lookup is performed by key key-ed map is often used as implementation may be used to pass information to objects without lookup evaluation global object – creates external dependencies may be preferred to passing them around as parameters

Registry Review why is it called a non-canonical pattern? what is Registry and what kind of functionality should it provide? where and how should Registry be used? Registry is a global object. How is this implemented in C++? why can’t just a global queue be used to implement the functionality of a Registry? What’s wrong with using Registry and why is it used anyway?