Swift uses ARC (Automatic Reference Counting) similar to Objective-C to track and manage application memory. In most cases, we don’t need to bother about memory management by ourselves, the swift compiler will take care of it. But there are some cases where we need to deal with it by ourselves. I am going to discuss some of the common cases from those.
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 iOS we always end up defining our instance variables as @property (strong) or @property(weak). But what does strong and weak mean, and when to use which one?
In cocoa, an objects memory is managed via a system called retain count. When an object is initialized, its retain count is increased by 1 from zero. And each time it is strongly referenced by someone, the retain count keeps increasing by 1. In ARC (a compile time feature of Apple’s version of automated memory management, acronym of Automatic Reference Counting), it only frees up memory for objects when there are zero strong references to them, or simply put, the retain count is zero.
Using delegates in iOS and Cocoa is a very basic and fundamental part and we use them very frequently in our codes. As like in business, cocoa uses delegates as a formal way to pass work/data from one object to another. 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 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 contractor of the later one by signing a contract called protocols (as defined in cocoa).