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The observer design pattern is a behavioural pattern listed among the 23 well-known "Gang of Four" design patterns that address recurring design challenges in order to design flexible and reusable object-oriented software, yielding objects that are easier to implement, change, test and reuse.
Observer pattern a.k.a. Publish/Subscribe or Event Listener. Objects register to observe an event that may be raised by another object Weak reference pattern De-couple an observer from an observable [2] Protocol stack Communications are handled by multiple layers, which form an encapsulation hierarchy [3] Scheduled-task pattern
The Python example is incorrect in the same way as the Delphi example; The C# example is incorrect: it has a "message" payload which is an Event-Driven concept, not Observer Pattern. The Subject doesn't have any internal data state, instead it's used as a Publish point with SendMessage to the Subscribed objects.
Entity–component–system (ECS) is a software architectural pattern mostly used in video game development for the representation of game world objects. An ECS comprises entities composed from components of data, with systems which operate on the components.
For example, a simple linearized object would consist of a length field, a code point identifying the class, and a data value. A more complex example would be a command consisting of the length and code point of the command and values consisting of linearized objects representing the command's parameters.
Design Patterns: Elements of Reusable Object-Oriented Software (1994) is a software engineering book describing software design patterns.The book was written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, with a foreword by Grady Booch.
ReactiveX is a combination of ideas from the observer and the iterator patterns and from functional programming. [2] An observer subscribes to an observable sequence. The sequence then sends the items to the observer one at a time, usually by calling the provided callback function. The observer handles each one before processing the next one.
Iterator pattern – defines a traversal principle like the visitor pattern, without making a type differentiation within the traversed objects Church encoding – a related concept from functional programming, in which tagged union/sum types may be modeled using the behaviors of "visitors" on such types, and which enables the visitor pattern ...