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Design patterns in iOS!

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Mithin Thomas,Mobility Lead

What is a design pattern?

Developers encounter many problems during software development. It is likely that earlier developers had faced similar issues and had used various solutions to solve them. Such time-tested solutions to recurring design problems are commonly known as design patterns. More than solving problems that software developers face during development it ensures that a developer does not have to re-invent the wheel for every situation.


Why should we use design pattern?

Design patterns are common solutions for commonly occurring problem within a given context in software design.  They help speed up the development process by providing tested and proven development paradigms. Since they are already widely used and well documented, developers can easily learn and chances of technical risk is very low.


Please note, design patterns are not finished designs; these are descriptions or templates for how to solve problems that can be used in many different situations.  They are therefore highly flexible and can be applied to any language that supports object-orientation methodology. This gives the developers a common vocabulary of high-level ideas with minimal explanation and full understanding.


What are the design patterns in iOS

iOS developers often face similar problems over and over again. This approach of using Design Patterns helps engineers find and solve these problems before development begins.  Cocoa is built and encouraged to use tons of design patterns.


The commonly used design patterns are listed below:


MVC (Model View Controller)

The Model-View-Controller (MVC) design pattern is considered one of the building blocks of Cocoa for iOS app development. MVC is a concept which separate out the application’s concerns. As the name suggests it divides a given software application into three interconnected parts – Model, view and Controller. This way it separates internal representations of information from the ways that information is presented to or accepted from the user.


Model Objects: Represents the data.

View: Interface that the user views and interacts with.

Controller: Mediator that coordinates all the work.



Delegate is a design pattern which helps to connect objects and helps them to communicate with each other. It is a mechanism in which an object acts on behalf of, or in coordination with, another object. A delegate allows one object to send messages to another object when an event happens.



This pattern involves a single class which is responsible to create an object while making sure that only single object gets created. Only one copy of this object exists and the state is shared and reachable by any other object.


The goal is to ultimately create code that is loosely coupled, reusable, and readable. A developer looking at another’s code should instantly understand it and also what each class does in the application. It is important to be aware of design patterns when you consider how to solve a particular problem, especially in the early stages of designing your app. It will contribute a lot towards code quality. 

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