Code Freely, Live Fully
Code Freely, Live Fully
Introduction The observer pattern is a software design pattern that allows an object, usually called the subject, to maintain a list of dependents, called observers, and notify them automatically of any state-changes. Many languages have this pattern either built-in or…
Introduction You can use the memento pattern to (partially) expose the internal state of an object. One use case for this pattern is to serialize an object to a file or as JSON for example, another is to build an…
Introduction In Design Patterns, the Iterator is a way of traversing over a container, that is access each of the container’s elements. It is used as a convenient way to traverse over lists or arrays, but it could also be…
Introduction The flyweight pattern is a pattern that helps minimize memory usage by sharing and reusing data. A common example is wordprocessor where each character not only holds the character like ‘A’ but also things like markup and formatting data.…
Introduction The Interpreter pattern can be used to interpret and evaluate sentences in a language. The idea is to make a class for each symbol, both terminal and non-terminal and construct a syntax tree which can be evaluated and interpreted.…
Introduction The facade pattern is used as a way to hide more complex logic. A facade can do the following: A facade pattern is typically used in the following cases: This might all sound quite complex, here is what it…
Introduction The prototype-pattern is a creational design pattern that allows us to create new objects by cloning existing ones, i.e. the existing objects function as a kind of template. This can save time in some cases when for example an…
Introduction The Adapter pattern is used to make one interface compatible with another. It allows objects with different, and therefore incompatible interface to work together. If you for example want to bring an existing class into your system with an…
Introduction The proxy-pattern is a very useful design pattern. The basic function is to make sure that a caller has no direct access to the instance of an object but rather goes through another class which does have access. I…
Introduction The mediator pattern is a pattern used when you want to simplify communication i.e. message dispatching in complex applications. It involves building a mediator where each objects can delegate its communication, and which routes the messages to the right…
Introduction The strategy pattern is a behavorial design pattern that allows you to define a family of algorithms, encapsulate them as an object, and with the help of interfaces make them interchangeable. The use of type annotations also helps to…
Introduction The builder pattern is a creational design pattern, i.e. it is a pattern for creating or instantiang objects of classes. It is used for breaking down the construction process, into smaller, more manageable and testable steps. It looks like…
Introduction The visitor pattern is a design pattern that allows for adding new operations to a collection of objects, without, and that is important, modifying the objects themselves. It looks like this: There are two main functionalities: Implementation in Python…
Introduction The command pattern is a behavioral design pattern. It is used by an Invoker to perform one action or a series of actions on objects, called Receivers. The Invoker is unaware of the nature of the receiving objects, it just knows about…
Introduction The singleton pattern restricts the instantiation of a class to a single instance. The singleton pattern makes it possible to ensure that: One of the main uses of the singleton pattern is logging, as all clients who wish to…