TOP-14 Interview Questions in Swift for Beginners - ByteScout
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TOP-14 Interview Questions in Swift for Beginners

Swift is a programming language used to develop software owned by Apple Inc. like macOS, tvOS. Programming using swift is fun and easy to use and has gained popularity over the years. So, you may be asked questions about Swift if you go to a job interview. To help you out, here are the top interview questions in Swift for beginners.

Interview Questions in Swift for Beginners

1. Define Swift and its differences compared to Objective-C

Answer: Both Swift and Objective-C are used to develop iOS programs. However, Swift is an open-source programming language, unlike Objective-C.

Swift has a clear and easy syntax, and the overall program remains brief, making reading and maintenance easier, unlike Objective C, which is comparatively hard to use.

Swift focuses on rationality and precision, making the code smaller, unlike Objective C, which can be twice as big as a similar Swift code.

You can compile Swift programs as a dynamic framework, unlike Objective C, which cannot be compiled into static libraries and dynamic frameworks.

2. Advantages of using Swift

Answer: Swift is an open-source code, making it available for everyone, and it makes upgrading of the codes easier.

Swift is simpler and more accurate compared to conventional programming languages like C and C++. Since Swift borrows syntaxes from other programming languages, it is more meaningful.  In swift, all the content of the implementation (.m) and header (.h) files are combined in a single file, that is (.swift).

Swift is supported by multiple devices and is not restricted to Apple devices.

Swift can support dynamic libraries, which greatly reduces space complexity and enhances performance.

Swift supports optional data type which can be held either as a value or not.

3. Where to test iPhone apps if you do not have an iOS device

Answer: In the absence of an iOS device, we will test our application on simulators provided by Apple on the Mac system.

4. How to declare an optional property in Swift?

Answer: We have to declare a question mark ??’ within the code to form a property optional. If a property doesn’t have any value stored in it, then the symbol ‘?’ helps to avoid semantic errors.

5. What are functions in Swift

Answer: Functions are a set of codes that perform a specific function and can be called anytime within the program. In the Swift programming language, functions are used to pass both local and global parameter values when the function is invoked.

In Swift4, functions are often categorized into two types:

  • User-Defined Functions
  • Built-in Functions (Library Functions)

6. What kind of language is Swift

Answer: Swift is an open-source, object-oriented programming language.

7. Define the common execution states for a Swift iOS App

Answer: The five common execution states are as follows:

  • Not Running: This is often a simple state during which our app isn’t launched, or no code is being executed and terminated by the system, and therefore the application is totally switched off.
  • Inactive: This state is simply a transitional state. An inactive state means our application is running within the background but isn’t ready to receive events.
  • Active: Active state is that the main execution state, where our app is running within the background and is in a position to receive events.
  • Background: This is often the state where our App is running within the background and still is in a position to execute the code within the background.
  • Suspended: This state means our app running is within the background state, and therefore the system suspends this app, and the application cannot execute any code.

8. State and explain the basic data types in Swift

Answer: The int data type stores integer values in the allocated memory.

The double and float data type stores decimal values in the allocated memory.

The string data type holds a text enclosed in double-quotes.

The bool data type stores Boolean values 0 (False) and 1 (True).

Array data type contains values of a similar data type.

Dictionary data type contains an unordered collection of similar data types and is connected with a unique key.

9. State the different types of literals present in Swift language

Answer: A Swift literal may be defined as a direct value of a variable or a constant.  It can be a number, character, or string. We use literals to initialize or assign value to variables or constants.

The different types of literals are:

  • Binary Literals
  • Octal Literals
  • Hexadecimal Literals
  • Decimal Literals

10. How to write comments in Swift

Answer: There are two ways to write comments in Swift. You can write single-line comments using double slashes (//). Or, you can write multiline comments. Multiline comments start with /* and end with */.

11. Define lazy stored procedure and its utilization

Answer: Lazy stored properties are used for a property whose initial values aren’t calculated until the first time it’s used. A lazy stored property is often declared by writing the lazy modifier before its declaration. Lazy properties are useful when the initial value for a property relies on outside factors whose values are unknown.

12. Which JSON framework is supported by iOS

Answer: iOS supports the SBJSON framework. SBJSON framework provides additional control and a versatile API which makes JSON handling easier. It’s a well and highly flexible framework that supports the flexible functioning of APIs.

13. Define Protocol in Swift

Answer: The concept of a protocol is similar in Swift and Java. It is a common feature in the Swift programming language. It defines a blueprint of methods, properties, and other things that are required for a specific task.

In simple words, a protocol is an interface used to describe some methods and properties. You can implement properties by defining enumerations, functions, and classes.

Protocols are declared after the structure, enumeration, or class type names. Single and multiple protocol declarations are often possible. Multiple protocols are separated by commas.

14. State the difference between classes and structures

Answer: Classes can support inheritance, unlike structures. Classes are also called reference types, whereas structures are value types.


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