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What design patterns are commonly utilized  and used in iOS apps?

Ans: Design pattern in iOS : Typical commonly used patterns when building iOS applications are people who Apple advocates for in their Cocoa, Cocoa Touch, Objective-C, and Swift documentation. These are the patterns that each iOS developer learns.

iOS design patterns used are

  • MVC
  • Singleton
  • Delegate
  • Observer.


The good old Model-View-Controller is Apple’s go-to application architecture design pattern. It’s good for small/simple apps, but not sustainable within the long term. We’ll cover it in additional details within the following section.


This is a standard OOP design pattern where you create the one and only in- stance of a category that may be used everywhere within the application where an in- stance of that class is important.

this is often a useful design pattern but commonly overused to the purpose of becoming an anti-pattern. the most issue is that developers often use singletons to store a worldwide state which isn’t an honest idea because of race conditions and other varieties of data overrides that inevitably happen.


Delegate is one in all the core Cocoa design patterns. it’s a variation of the Ob- server pattern where just one object can observe or be delegated to events from another object.

It’s a one-to-one relationship that’s implemented through protocols. Cocoa itself uses this pattern plenty with UITableViewDelegate, UITableViewDataSource, UIPickerViewDelegate, and similar proto- cols that are exposed by the framework for developers to use.


This pattern may be a common one in iOS. It’s a design pattern that helps objects ob- serve state changes or events in other objects without coupling that observation to internal implementation of these objects.

Developers can always implement the Observer pattern themselves, but there are two built-in implementations in Cocoa already – Delegate, one-to-one observation, and KVO (key-value ob- serving), one-to-many observation.

Red Flag:

ios design patterns :When interviewer asks this question (in one form or another) what they’re trying to find are some things besides MVC. Because MVC is that the go-to design pattern, the expectation is that each iOS developer knows what it’s. What they need to listen to from you though, is what else is usually used and available out of the box.

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