Interpreter Design Pattern
Problem “If a particular kind of problem occurs often enough, then in might be worthwhile to express [the] instances of a problem as sentences in a simple language.” The example is pattern matching...
View ArticleMemento Design Pattern
Problem When a user interacts with a program, one of the important features is sometimes the ability to undo what was just done. This is common in many applications from graphics to word processing. In...
View ArticleMediator Design Pattern
Mediator Design Pattern Problem Partitioning a system can increase reusability. However, if as the number of classes increases then number of interconnections also increase that reduces the...
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Iterator Design Pattern
Iterator Design Pattern Problem When working with lists it is often nice not to have to know the internal details of how the list is implemented. We may have different ways to traverse the list and do...
View ArticleTemplate Method Design Pattern
Template Method Design Pattern Problem It is often tedious to implement many subclasses of a particular base class. It would be nice if there were a way to reference the existing structure, and only...
View ArticleState Design Pattern
Problem When an object has different internal states, how can we implement the states without complicated boolean logic inside the class? Solution The answer is the state design pattern. In this...
View ArticleStrategy Design Pattern
Strategy Design Pattern Problem How can we gain the ability to use different algorithms for like functionality, having the clients contain the code that implements the algorithms? How can we facilitate...
View ArticleCommand Design Pattern
Problem How can we issue request to other objects in a system, without having to know who will receive the request, or even what the request is? This can be useful for implementing functionality such...
View ArticleChain of Responsibility Design Pattern
Chain of Responsibility Design Pattern Problem Consider the case where you have a structural hierarchy of object that is not necessarily subclasses from the same base class. Now lets say there is a...
View ArticleVisitor Design Pattern
Visitor Design Pattern Problem Sometimes we have multiple operations that need to be implemented on a structure of objects. Traditionally we would implement each of the objects to derive of a base...
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