We all have been through situations, where we had to create classes with multiple constructors or constructor with a lot of dependencies (parameters). These classes tend to get bloated quickly with the over used constructor methods and too many parameters and starts messing with the default properties values. Whenever you find yourself into this situation you; my friend; have been trapped by a notorious anti-pattern called Telescopic Constructors or, Telescopic Initializers. The initial intention of this pattern was to simplify the process of working with classes with a lot of initializer parameters.
While talking about design patterns, most developers have fumbled upon this one; especially cocoa developers (both iOS and Mac application developers). Singletons are the most common design pattern you’ll come to see in Cocoa and CocoaTouch frameworks. They are literally everywhere; i.e. UIApplication.shared, UIScreen.main, NotificationCenter.default, UserDefaults.standard, FileManager.default, URLSession.shared, SKPaymentQueue.default() and many more. So, what are Singletons? And why are they so special?
In real life software development one particular challenge we developers constantly face is requirement changes. Anyone who is in the software business game knows how frequently and drastically software specification can change in any time. For this reason, in software engineering only one thing is considered as constant: CHANGE!
In object oriented world, we have some nice ways to deal with this, i.e. design patterns to the rescue. There are lots and lots of design patterns out there to help us, the developers. Amongst them the most common and widely used one is known as Strategy Pattern. Any developer with a few years of experience under his/her belt uses this quite frequently (sometimes even without knowing they are using it!).
In this post I am going to try to create a scenario, which we can solve using strategy pattern.
Using delegates in iOS and Cocoa is a very basic and fundamental part and we use them quite frequently in our codes. As like in business, cocoa uses delegates as a formal way to pass data(job) from one object(client) to another(vendor). In business, you want to do make something but you need raw materials to do so. So you ask the supplier to give you raw materials and you sign a contract for that. Same thing goes in cocoa, a class that wants to perform a task that depends on the response of another class acts as the delegate to the later. The first class wants to be the vendor of the later one by signing a contract called protocols (as defined in cocoa).