Swift programmer Interview Questions and answer

Swift programmer Interview Questions and answer

Swift programmer Interview Questions and answer

Swift is a powerful and intuitive programming language for iOS, iPadOS, macOS, tvOS, and watchOS. Coding in Swift is quite interactive and fun, the syntax is concise yet expressive, and Swift includes modern features developers love. Swift code is safe by design, yet also produces software that runs lightning-fast.

Swift is the result of the latest research on programming languages, combined with decades of experience building Apple platforms. Named parameters are expressed in a clean syntax that makes APIs in Swift even easier to read and maintain. And here’s something more interesting, you don’t even need to type semi-colons

Swift programmer Interview Questions and answer


Being a developer friendly language it invites lot of audience and is being quite enormously amongst the developers. So if you are planning to prepare for an Interview on the same,

Here are some Swift programming Interview Questions and answer:


1.) What is iOS Swift ?

Swift is a compiled and new programming language evolved by Apple Inc in June 2014 in order to develop apps for mobile and desktop. This language works for watchOS, macOS, iOS, and tvOS.

Apple created Swift language to work with both Cocoa Touch and Cocoa. Swift supports multiple operating systems such as Free BSD, Linux, Darwin, etc. This language is design to work along with the Objective-C library and Cocoa framework in the Apple products.


2.) What is the difference between Upcast and Downcast in Swift?

The upcast, going from a derived class to a base class, can be checked at compile time and will never fail. However, downcasts can fail since you can’t always be sure about the specific class.
If you have a UIView, it’s possible it’s a UITableView or maybe a UIButton.

  • downcasts must be either optional with as? or
  • “forced failable” with as! when sure about the type


3.) What are some of the major advantages of using Swift?

There are some important advantages of developing apps for macOS and iOS using swift.

  • Open-source language: The Swift programming language has been created as an open-source and is being open to everyone, this makes it simple for the program to upgrade all the source codes, email lists and bug tracker at regular intervals.

  • Easy to learn and maintain: Swift programing language is more simple and accurate when compared to C/C++. Apple evolved its programing language to be easy to use and syntaxes are taken from programming languages such as C#, Python, and Ruby. These simple syntax of this programing language make it more meaningful. In swift, all the content of the implementation (.m) and header (.h) files are combined in a single file that is (.swift).

  • Supported by multiple devices: Swift programming language is not just limited to support Apple devices, it will also support multiple devices of the technology world like Linux and Windows devices.

  • Supports dynamic libraries: Dynamic libraries are the executable chunks of the code that can be connected to an app. This feature allows the latest swift programing language. In swift, dynamic libraries are directly uploaded to the memory, thereby resulting in deduction down on the initial size of the app and finally increases app performance.

  • Optional types: An optional in swift is a type that can be held either as a value or not. To declare an optional, we can use a question “?” mark.
  • Closures: Closures are self-contained blocks of functionality that can be passed around and used in our code.


4.) What is the difference between == and === ?

== operator checks if the values are the same, comparing value types“equal to”

=== operator checks if the references point the same instance (both point to the same memory address), comparing reference types“identical to”


5.) What do Classes and Structs have in common in Swift and what are the major differences?

The features classes and structs have in common:

  • Both structs and classes can define properties to store values, and they can define functions
  • They can define subscripts to provide access to values with subscript syntax
  • Can define initializers to set up their initial state, with init()

Classes support a few more capabilities that structs don’t have:

  • They can inherit from another class, like you inherit from UIViewController to create your own view controller subclass
  • They can be deinitialized, i.e. you can invoke a deinit() function before the class is destroyed

  • Classes are reference types and structs are value types
    • Value Type: When you copy a value type (i.e., when it’s assigned, initialized or passed into a function), each instance keeps a unique copy of the data. If you change one instance, the other doesn’t change too.
    • Reference Type: When you copy a reference type, each instance shares the data. The reference itself is copied, but not the data it references. When you change one, the other changes too.


6.) Which JSON framework iOS supports ?

iOS supports SBJson framework. SBJson framework provides additional control and a flexible API which makes JSON handling easier. Also it is a well and highly flexible framework that supports the flexible functioning of APIs.


7.) What’s the difference between a class and a protocol ?

In their basic form, a protocol describes what an unknown type of object can do. You might say it has two or three properties of various types, plus methods. But that protocol never includes anything inside the methods, or provides actual storage for the properties.

In a more advanced form, you can write extensions on your protocols that provide default implementations of the methods. You still can’t provide storage for properties, however.

In comparison, classes are concrete things. While they might adopt protocols – i.e., say they implement the essential properties and methods – they aren’t essential to do that. You can create objects from classes, whereas protocols are just type definitions. Try to think of protocols as being abstract definitions, whereas classes and structs are real things you can create.


8.) When is ‘Set’ preferred over an array in Swift?

One should use a set rather than an array if all the following criteria are true:

  1. You intend to add each item only once. Sets never allow duplicates.
  2. You don’t care about the order of the items in the set.
  3. You don’t need to use APIs that require arrays.
  4. You’re storing Hashable types, either your own or one of Swift’s built-in types likes strings and integers. Sets use hash values for fast look up of items.


9.) What is Protocol?

The protocol is a very common feature of the Swift programming language and the protocol is a concept that is similar to an interface from java. A protocol defines a blueprint of properties, methods, and other requirements that are suitable for a particular task.

In its simplest form, the protocol is an interface that describes some methods and properties. The protocol are just the properties or methods skeleton instead of implementation. Moreover, Properties and methods implements by defining enumerations, functions, and classes.

Also Protocols declaration is after the structure, enumeration or class type names. A single and multiple protocol declaration can be possible. Commas differentiate Multiple protocols.


10.) What are the different collection types in Swift?

There are three primary collection types that are available in swift for storing a collection of values. They are dictionaries, sets, and arrays

  1. Arrays: Arrays is an ordered collection of values, which is stored in the same type of values in an ordered list.
  2. Sets: Sets are an unordered collection of unique values, which are stored in a distinct value of the same type in a collection without any defined ordering.
  3. Dictionaries: Dictionaries are an unordered collection of Key and value pair associations in an unordered manner.

So these were some of the important Swift programming Interview Questions and answer

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