Swift Interview Questions

Swift Interview Questions Download Swift Interview Questions PDF

Swift Interview Questions

Swift utilizes the standard set of basic data types for different purposes such as numbers, Boolean values, and strings.

1.Int: Int is used to store the integer value. On 32-bit devices, it is always 32 bits deep and on 64-bit devices, it has 64 bits deep. You are able to access the maximum and minimum values the type enable store with the help of the min and max static properties:

println("\(Int.min)")
//output on 32-bit device: -2147483648
//output on 64-bit device: -9223372036854775808
println("\(Int.max)")
//output on 32-bit device: 2147483647
//output on a 64-bit device: 9223372036854775807

2. Double and Float: The use of Float and Double in Swift is considered when you are used to working with the decimal number. Double will be always 64-bit whereas float is always a 32- bit value. It does not depend upon the architecture of the device. The compiler utilizes the Double type instead of a Float in case of using decimal literal values. So, if you don't need the value of a 64-bit value, then it is definitely that you declare

Float variable.

var distance = 0.0 //distance is a Double var seconds: Float = 0.0 // second is a Float

3. Bool: The Bool basic type is used to store the Boolean value. The main difference between the Objective-C and Swift is it uses true and false instead of YES and NO as in Objective-C

It is unable to compare the value to 0 or nil in Swift. The expression that can definitely retort a Bool cam come into used to describe a boot value. Let's take an example

var someInteger = 0
var hasSome:Bool = (someInteger != 0)
//hasSome: false
someInteger = 100
hasSome = (someInteger != 0)
//hasSome = true

4. Strings: String literals are the text that is enclosed by double quotes in Swift. var greetingString = "I am Rich"

A string is the factory of the characters and the character pictures a Unicode character, has symbols, one of more than 100 scripts and 110,000 characters. There are a large number of character encoding method to implement the characters like UTF-8 or UTF-16. These encoding methods store every character with the help of a variable number of bytes in memory.

5. Arrays: In Swift, arrays are the collection types. It is an arranged list of the items of the equal type. At the time of declaring an array in Swift, you need to specify what type it will contain. When it is done, it is able to contain only that type. This whole process is to help you in ensuring the expected guaranteed type when you pull an item out of the array. You enclosed a list of elements with square brackets to create an array literal. For example var dogs = ["Harlow", "Cliff", "Rusty", "Mia", "Bailey"]

You need to assure that all the should be of equal types or else you will get a compile-time error.

It consists of two ways to represent that is long form and short form. Both the ways are comparable can be used mutually

Long form: Array Short form: [ValueType]

6. Dictionaries: A dictionary is an unordered factory of items of a particular type and every type is connected with a unique key. Like the arrays, it also contains the two ways to represent the type: the short form and the long form. Both of these types are comparable and can be used mutually.

Long form: Dictionary<KeyType, ValueType>
Short form: [KeyType: ValueType]
Here is an example of syntax to declare and initialize a dictionary with the use of short form.
var people: [String:SomePersonClass] = [:] //explicit type
//or, alternately
var people = [String:SomePersonClass]() //implicit type

Follow the following steps:

Step 1: Add Objective-C Implementation --.m: First of all, add a .m file to the class and then name it CustomObject.m.

Step 2: Add Bridging Header: At the time of adding your .m file, you receive a prompt with three options of YES, NO and cancel. You need to select YES

Step 3: Add Objective-C Header --.h: After that Add one more .h file and name it CustomObject.h.

Step 4: Build your Objective-C Class

In CustomObject.h

#import <Foundation/Foundation.h>
@interface CustomObject : NSObject
@property (strong, nonatomic) id someProperty;
- (void) someMethod;
@end
In CustomObject.m
#import "CustomObject.h"
@implementation CustomObject 
- (void) someMethod {
    NSLog(@"SomeMethod Ran");
}
@end

Step 5: The next step is to add Class to Bridging-Header

In YourProject-Bridging-Header.h

#import "CustomObject.h"

Step 6: At last, use your Object

In SomeSwiftFile.swift:

var instanceOfCustomObject: CustomObject = CustomObject()

instanceOfCustomObject.someProperty = "Hello World"

println(instanceOfCustomObject.someProperty)

instanceOfCustomObject.someMethod()

In the bridging header, there is no need to import explicitly.

Some control statements are:

  • Control flow statements as the name suggests are efficient to check the course of execution in a program. There are several kinds of control transfer statements are present in Swift such as loop branch statement, loop statement, and control transfer statement
  • Loop branch permit a block of code to be executed time and again
  • Branch statements permit a particular block of code to be executed only if some circumstances are satisfied,
  • Control transfer statements present a method to change the system in which code is executed.

In-out parameter lets you change the value of a function parameter from within the body of that function.

Adapter – It lets the classes with incompatible interfaces to work together and it wraps itself around the object to expose a standard interface to interact with that object.Memento – This pattern in iOS is used as a part of state restoration.

That is this externalized state can be restored without violating any encapsulation.This pattern is especially used for the archiving in Apple.

Generic is efficient to write sensitive and reusable functions and types. It is provided in Swift 4. Most of the people use this feature to evade the risk of duplication. 'Arrays' and 'Dictionary' are also referred to generic collection. The libraries of Swift 4 are comprised of generic code.

You can add generics to a method (function) but can’t add to a variable. Understand it with an example:

func Vector3D(x: [T], y: [T], z: [T])
 {    self.xCord = x
    self.yCord = y
    self.zCord = z}

In this example, the generic created here is in a function. You can change the T with anything you want. This is how you can add generic in function.

The multiple line comment is written in between the symbols (/*) at the start and (*/) at the end.

A tuple is used to arrange multiple values in a single compound Value. In tuple, it is not compulsory for value to be of the same type. It can be of any type.

For an instance, ("interview", 123) is a tuple having two values: one is string Type, and another one is an integer type.

To create a tuple: To create it, you should have tuple literals which are a list of values listed in tuple separated by the comma. For example, the point is a tuple created by tuple literals written in between a pair of parentheses. To change a tuple literal, use dot notation with tuple’s name and assign the desired value. Check example:

var point = (0, 0)
point.0 = 10
point.1 = 15
point // (10, 15)
  • Typecasting Patterns – This pattern allows you to match or cast the types.
  • Wildcard Patterns – This pattern matches as well as ignores any kind and type of value.
  • Optional Patterns – This pattern is used to match the optional values.
The classes are not inherited directly from the base class in the Swift programming language.The classes defined by the developer without specifying the superclass becomes the base class automatically.

Both the terms 'let' and 'var' are used for declaring the functions in JavaScript but the main difference between these two terms is that the 'let' is block scoped while a 'var' is the functional scope. It is not wrong to say that a variable represented with var is defined throughout the program in relation to let

Example of var:

Input: 
console.log(x); 
var x=5; 
console.log(x); 
Output: undefined 5

Example of let:

Input: 
console.log(x); 
let x=5; console.l
og(x); 
Output: Error

Higher order functions are those in which you can pass a function as an argument and returns a function as a result. There are many benefits to using them:

  • They provide flexibility but compromises with complexity.
  • They are useful in asynchronous communications in which simple functions can’t be used.
  • They improve the readability of code and decreases the length of the code.