50 iOS Interview Questions And Answers

Durul Dalkanat
11 min readDec 27, 2016

1- How could you set up Live Rendering?
The attribute @IBDesignable lets Interface Builder perform live updates on a particular view. IBDesignable requires Init frame to be defined as well in UIView class.

2- What is the difference between Synchronous & Asynchronous task?
Synchronous: waits until the task have completed Asynchronous: completes a task in the background and can notify you when complete

3- Explain Compilation Conditions

Compilation Conditions to use if DEBUG … endif structure to include or disable given block of code ve separate targets.

4- What is made up of NSError object?
There are three parts of NSError object a domain, an error code, and a user info dictionary. The domain is a string that identifies what categories of errors this error is coming from.

5- What is Enum or Enumerations?

According to Apple’s Swift documentation:

Managing state, the bits of data that keep track of how the app is being used at the moment, is an important part of a developing your app. Because enumerations define a finite number of states, and can bundle associated values with each individual state, you can use them to model the state of your app and its internal processes.

Enum is a type that basically contains a group of related values in the same umbrella but case-less enum won’t allow us to create an instance.

Reference: https://developer.apple.com/documentation/swift/maintaining_state_in_your_apps

6- What is the bounding box?
The bounding box is a term used in geometry; it refers to the smallest measure (area or volume) within which a given set of points.

7- Why don’t we use strong for enum property in Objective-C?
Because enums aren’t objects, so we don’t specify strong or weak here.