Top Swift Interview Questions
[quote font=”verdana”]What is iOS Swift?[/quote]
Swift is a compiled and new programming language evolved by Apple Inc in June 2014 in order to develop apps for mobile and desktop applications. 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 was designed to work along with the Objective-C library and Cocoa framework in the Apple products.
[quote font=”verdana”]What are the advantages of using Swift?[/quote]
Swift programming language has speedily become one of the quick-growing languages in memoir. Swift makes us develop software that is incredibly fast, robust and secure.
This language is the most useful programming language that is used to develop an application for macOS and iOS(iPad and iPhone).
There are some important advantages offered by developing apps for macOS and iOS using swift.
- Open-source language: The Swift programming language has been created in 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 trackers 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 only, 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.,
[quote font=”verdana”]Explain Swift vs Objective-C.[/quote]
Enlisted below are the various differences between Swift vs Objective-C.
- Swift is an object-oriented and functional programing language, whereas Objective-C is a class-based object-oriented programing language.
- Swift supports dynamic libraries, whereas Objective-C does not support dynamic libraries.
- Swift supports Tuples, whereas Objective-C does not support Tuples.
- Semicolons are not required in Swift, whereas semicolons are required in Objective-C.
- Swift is an open-source programing language, whereas Objective-C is limited to apple, and it’s not an open-source language.
- We have to use “let” keyword to declare for constant and “var” keyword to declare for a variable, whereas in objective C, we have to declare the variable as “NSString” and constant as “int”.
- Swift enables us to define methods in structure, classes or enumeration, whereas Objective C does not allow this.
- In swift, we can define classes in a single file (.swift), whereas in Objective C we create separate interface (.h) files for classes and implementation (.m) files for classes.
[quote font=”verdana”]What are the most important features of swift?[/quote]
Some important features of swift are given below:
- More impressive structs and enums
- Protocol oriented
- Optional Types
- Type Safety and Type inference language
- Not required to use semicolons
- Enforced initializers
- Safe by default
- Less code, fewer files
- Forced Unwrapping
- Tuples
- Closures
- Much faster when compared to other languages.
[quote font=”verdana”]Is Swift an object-oriented programming language?[/quote]
Yes, Swift is an object-oriented programming language.
[quote font=”verdana”]What type of objects are basic data types in swift?[/quote]
Swift uses a standard set of basic data types for different purposes such as Boolean values, numbers, and strings.
- Int: int is used to store the integer value.
- Double and Float: Double and Float in swift are considered when we work with the decimal numbers.
- Bool: The bool type is used to store the Boolean value. In swift, it uses true and false conditions.
- String: In String literals, the user defines the text that is enclosed by double quotes in Swift.
- Arrays: Arrays are the collection of list items.
- Dictionaries: A dictionary is an unordered collection of items of a particular type that is connected with a unique key.
[quote font=”verdana”]What is init() in Swift?[/quote]
Initialization is a process of preparing an instance of an enumeration, structure or class for use. Initializers are also called to create a new instance of a particular type. An initializer is an instance method with no parameters. Using the initializer, we write the init keyword.
init()
{
// perform some New Instance initialization here
}
[quote font=”verdana”]What are the control transfer statements that are used in iOS swift?[/quote]
The control transfer statements that are used in iOS swift include:
- return
- break
- continue
- fallthrough
[quote font=”verdana”]What is the difference between Let and Var in swift?[/quote]
In swift language, we can declare a constant and variable using Let and Var keyword.
let: Let keyword is immutable, it’s used to declare a constant variable, and the constant variable cannot be changed once they are initialized. For Example We cannot change the value of age, you can declare the constant value of it only once using the let keyword.
var: Var keyword is mutable, and is used to declare a variant variable. These variant variables can change the run time. For Example
Swift Interview Questions
[quote font=”verdana”]How to add an element into an Array?[/quote]
Arrays are one of the most generally used data types in an application (app). We use arrays to organize our application (app) data. Swift makes it easy to create an array in our code using an array literal. Array elements are simply surrounded by a comma and the list of values is separated with square brackets. For example or More information
[quote font=”verdana”]What is a dictionary?[/quote]
Dictionaries are an association of an unordered collection of key-value pairs. Each value is associated with a unique key, which is a hashable type such as a number or string. We can use the dictionaries concept in swift programming language whenever we want to obtain the values based on a key value.
For the syntax of Swift Dictionaries
[quote font=”verdana”]What is a Protocol in swift?[/quote]
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 is just described as the properties or methods skeleton instead of implementation. Properties and methods implementation can be done by defining enumerations, functions, and classes.
Protocols are declared after the structure, enumeration or class type names. A single and multiple protocol declaration can be possible. Multiple protocols are separated by commas.
[quote font=”verdana”]What is a delegate in swift?[/quote]
Delegate is a design pattern, which is used to pass the data or communication between structs or classes. Delegate allows sending a message from one object to another object when a specific event happens and is used for handling table view and Collection View events.
Delegates have one to one relationship and one to one communication.
[quote font=”verdana”]What is the use of double question mark “??” in swift?[/quote]
The double question mark “??” is a nil-coalescing operator, it is mainly a shorthand for the ternary conditional operator where we used to test for nil. A double question mark is also used to provide a default value for a variable.
stringVar ?? “default string”
This exactly does the common thing, if stringVar is not nil then it is returned, otherwise the “default string” is returned.
[quote font=”verdana”]What is a guard statement? What is the benefit of using guard statement in swift?[/quote]
A guard statement is used to transfer the program control out of the scope when one or more conditions are not met. Using the guard statement helps in avoiding the pyramid of doom.
[quote font=”verdana”]What are the collection types that are available in swift?[/quote]
Here are three primary collection types that are available in swift for storing a collection of values. They are dictionaries, sets, and arrays
- Arrays: Arrays is an ordered collection of values, which is stored in the same type of values in an ordered list.
- 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.
- Dictionaries: Dictionaries are an unordered collection of Key and value pair associations in an unordered manner.
[quote font=”verdana”]What is “defer”?[/quote]
The “defer” is a keyword that provides a block of code that can be executed while the execution is leaving the current scope.
[quote font=”verdana”]What is Tuple? How to create a Tuple in swift?[/quote]
A tuple is a group of different values in a single compound value. It is an ordered list of elements. There are two ways of accessing the object data in a tuple i.e. by name or by position.
In swift, a tuple can consist of multiple different types. It can support two values i.e. one of integer type, and the other of a string type. It is a legal command.
[quote font=”verdana”]What is the difference between Array and NSArray?[/quote]
The difference between Array and NSArray are given below:
- An array can hold only one type of data, whereas NSArray can hold different types of data.
- An array is a value type, whereas NSArray is an immutable reference type.
[quote font=”verdana”]What is the difference between class and structure?[/quote]
iOS Interview Questions
The difference between class and structure are given below:
- Classes are reference types, whereas structs are value types.
- Classes can be built on other classes, whereas struct cannot inherit from another struct.
- Classes have an inheritance, whereas structs cannot have an inheritance.
- In class, we can create an instance with “let” keywords and attempt to mutate its property, whereas there is no Mutability in Structs.
- Classes have Type Casting, whereas struct doesn’t have Type Casting.
[quote font=”verdana”]How to create a constant in Swift programming?[/quote]
We have to use the “let” keyword to declare a constant in the Swift Programming.
[quote font=”verdana”]How can we make a property Optional in swift?[/quote]
Declaring a Question mark “?” in the swift code can make a property optional. This question mark “?” helps to avoid the runtime error when a property doesn’t hold a value.
[quote font=”verdana”]How can we define a base class in swift?[/quote]
In a swift programming language, classes are not inherited from the base class. The classes are defined by the developer without specifying the superclass and it will become the base class automatically.
[quote font=”verdana”]How to write a multiple line comment in swift?[/quote]
A multiple line comment is written in between the (/*) at the starting point and (*/) at the endpoint.
[quote font=”verdana”]What is Optional chaining?[/quote]
Optional chaining is a useful process that we can use in combination with the optionals to call the methods, properties, and subscripts on the optionals and these values may or may not be nil. In this process, we may try to retrieve a value from a chain of the optional values.
- If the optional contains a value, then calling the subscript, method or property of an optional will return a value.
- If optional is nil, then calling the subscript, method and property will return nil.
[quote font=”verdana”]What is Optional binding?[/quote]
Optional Binding concept is used to find out whether an optional contains a value, and it makes that value available as a variable or temporary constant. We use an optional binding concept to check if the optional contains a value or not.
Optional binding can be used with the condition (if and while) statements to check for a value inside an optional.