Method A (naked parameters) always has the advantages that it requires the method author to type less, since they don’t have to implement a Parameter Object, it requires the method caller to type less, since they don’t have to instantiate a Parameter Object it performs better, since no Parameter Object has to be constructed and … Read more
A class implementing factory design pattern works as bridge between multiple classes. Consider an example of using multiple database servers like SQL Server and Oracle. If you are developing an application using SQL Server database as backend, but in future need to change backend database to oracle, you will need to modify all your code, … Read more
I don’t have Design Patterns: Elements of Reusable Object-Oriented Software in front of me at the moment, but I’m pretty sure the authors even say that the design patterns they present are a model that can be modified to fit a specific situation. This question cuts to the core of what a design pattern is … Read more
When it comes to smaller applications of this nature, I generally worry more about anti-patterns than I do about design patterns. That said, it’s really two sides to the same coin: the power of a design pattern for me is being familiar with them so as to recognize the less-than-obvious pros and cons of whatever … Read more
Prototype pattern Prototype results in a cloned object which is different from the original object. The state of the original is the same as the clone, at the time of cloning. Thereafter each object may undergo state change. You can think of this as something similar photocopying the original and then modifying the photocopy at … Read more
Best way to explain would be to take two examples from two categories. Composite from Structural patterns defines a tree like structure, so focuses on the relationship. One to many and has a type of relationships so that whole and part can be treated alike. Observer pattern on the other hand from Behavioral design patterns … Read more
Two patterns from Bill Venners; I think both are heavily used in ScalaTest: Stackable Trait (similar in structure to the decorator pattern, except it involves decoration for the purpose of class composition instead of object composition). Selfless Trait (allows library designers to provide services that their clients can access either through mixins or imports). Type … Read more
In functional programming, you would wrap a given function in a new function. To give a contrived Clojure example similar to the one quoted in your question: My original drawing function: (defn draw [& args] ; do some stuff ) My function wrappers: ; Add horizontal scrollbar (defn add-horizontal-scrollbar [draw-fn] (fn [& args] (draw-horizontal-scrollbar) (apply … Read more
That’s a great question since they are similar in that they provide an application access to a messaging system. It is how they acheive it I think that differentiates them. The Channel Adapter pattern deals how to get data from an existing system without modifying that system. Typically the Channel Adapdter is implemented out-of-process. Examples … Read more
In an optimistic update the UI behaves as though a change was successfully completed before receiving confirmation from the server that it actually was – it is being optimistic that it will eventually get the confirmation rather than an error. This allows for a more responsive user experience.