In Swift, we use the guard statement to transfer program control out of scope when certain conditions are not met. The guard statement is similar to the if statement with one major difference. The if statement runs when a certain condition is met. However, the guard statement runs when a certain condition is not met.
What is difference between if else and guard in Swift?
In if let , the defined let variables are available within the scope of that if condition but not in else condition or even below that. In guard let , the defined let variables are not available in the else condition but after that, it’s available throughout till the function ends or anything.
What is a guard statement?
Regardless of which programming language is used, a guard clause, guard code, or guard statement, is a check of integrity preconditions used to avoid errors during execution. A typical example is checking that a reference about to be processed is not null, which avoids null-pointer failures.
How does guard let work?
Swift gives us an alternative to if let called guard let , which also unwraps optionals if they contain a value, but works slightly differently: guard let is designed to exit the current function, loop, or condition if the check fails, so any values you unwrap using it will stay around after the check.
What are optionals in Swift?
An Optional is a type on its own, actually one of Swift 4’s new super-powered enums. It has two possible values, None and Some(T), where T is an associated value of the correct data type available in Swift 4.
Why guard is used in Swift?
In Swift, we use the guard statement to transfer program control out of scope when certain conditions are not met. The guard statement is similar to the if statement with one major difference. The if statement runs when a certain condition is met. However, the guard statement runs when a certain condition is not met.
What are closures in Swift?
In Swift, a closure is a special type of function without the function name. For example, { print(“Hello World”) } Here, we have created a closure that prints Hello World . Before you learn about closures, make sure to know about Swift Functions.
What are tuples in Swift?
In Swift, a tuple is a group of different values. And, each value inside a tuple can be of different data types. Suppose we need to store information about the name and price of a product, we can create a tuple with a value to store name (string) and another value to store price (float)
How do I unwrap optional in Swift?
Unwrapping in Swift is essentially verifying if the Optional value is nil or not, and then it performs a task only if it’s not nil.
You can perform unwrapping in the following ways:
- Using an if else block.
- Using Forced unwrapping.
- Using Optional binding.
- Using Optional chaining.
- Using a nil coalescing operator.
How do I use optionals in Swift?
You can simply represent a Data type as Optional by appending ! or ? to the Type . If an optional contains a value in it, it returns value as Optional
What is defer Swift?
The Swift defer statement is useful for cases where we need something done — no matter what — before exiting the scope. For example, defer can be handy when cleanup actions are performed multiple times, like closing a file or locking a lock, before exiting the scope.
What is @frozen in Swift?
Introduced with Swift 5, the @unknown attribute is particularly useful when switching over a nonfrozen enumeration. While the @frozen attribute is used on familiar enums such as Result or Optional within the standard library..
What is enum in Swift?
In Swift, an enum (short for enumeration) is a user-defined data type that has a fixed set of related values. We use the enum keyword to create an enum. For example, enum Season { case spring, summer, autumn, winter } Here, Season – name of the enum.
How if let works in Swift?
The “if let” allows us to unwrap optional values safely only when there is a value, and if not, the code block will not run. Simply put, its focus is on the “true” condition when a value exists.
What are higher order functions Swift?
Swift Higher-Order Functions
Higher-order functions are functions that take other functions or closures as arguments and that return a function or a closure.
What is size classes in Swift?
Size classes are traits assigned to user interface elements, like scenes or views. They provide a rough indication of the element’s size. Interface Builder lets you customize many of your layout’s features based on the current size class. The layout then automatically adapts as the size class changes.
What is singleton in Swift?
In Swift, Singleton is a design pattern that ensures a class can have only one object. Such a class is called singleton class.
What is continue in Swift?
The continue statement is used to skip the current iteration of the loop and the control flow of the program goes to the next iteration. The syntax of the continue statement is: continue. Before you learn about the continue statement, make sure you know about: Swift for loop.
Does Swift do keyword?
The do statement is used to introduce a new scope and can optionally contain one or more catch clauses, which contain patterns that match against defined error conditions. Variables and constants declared in the scope of a do statement can be accessed only within that scope.
What is array in Swift?
Specifically, you use the Array type to hold elements of a single type, the array’s Element type. An array can store any kind of elements—from integers to strings to classes. Swift makes it easy to create arrays in your code using an array literal: simply surround a comma-separated list of values with square brackets.
What is mutable in Swift?
In Swift, a variable is mutable whereas a constant is immutable. Xcode suggests turning the numberOfWheels constant into a variable by replacing the let keyword with the var keyword. In other words, Xcode suggests making numberOfWheels mutable. The value stored in a variable can be changed.
How many ways unwrap optional?
You can unwrap optionals in four ways: With force unwrapping, using if optional != nil and optional! With optional binding, using if let constant = optional {
What is the difference between optional none and nil?
There is no difference, as . none (basically it’s Optional. none ) and nil are equivalent to each other. The use of nil is more common and is the recommended convention.
What is Property Observer in Swift?
Property Observers. Property observers observe and respond to changes in a property’s value. Property observers are called every time a property’s value is set, even if the new value is the same as the property’s current value. You can add property observers in the following places: Stored properties that you define.
What is unconditional unwrapping in Swift?
Unconditional Unwrapping
When you’re certain that an instance of Optional contains a value, you can unconditionally unwrap the value by using the forced unwrap operator (postfix ! ). For example, the result of the failable Int initializer is unconditionally unwrapped in the example below.
Can any be optional Swift?
Swift doesn’t allow comparing Optional
What is multithreading in Swift?
Multithreading can be defined as the process which facilitates the CPU to create and execute concurrent threads. Typically, a CPU performs one operation at a time.
What is Rethrows in Swift?
Rethrows in Swift allows forwarding a thrown error by a given function parameter. It’s used a lot in methods like map , filter , and forEach and helps the compiler to determine whether or not a try prefix is needed. In my experience, you don’t have to write rethrowing methods that often.
What is static in Swift?
Swift allows us to use a static prefix on methods and properties to associate them with the type that they’re declared on rather than the instance. We can also use static properties to create singletons of our objects which, as you have probably heard before is a huge anti-pattern.
What is wrapping in Swift?
Wrapping means the actual value is stored in a logical outer structure. You cannot get to that value (in this case “moo”) without unwrapping it. In Swift world, it is always Christmas, and there are always presents — or at least variables — to unwrap. You unwrap values by adding exclamation points.
What is @discardableResult in Swift?
While writing methods in Swift you’re often running into scenarios in which you sometimes want to ignore the return value while in other cases you want to know the return value. The @discardableResult attribute allows us to enable both cases without having to deal with annoying warnings or underscore replacements.
What is mirror in Swift?
Reflection in Swift allows us to use the Mirror API to inspect and manipulate arbitrary values at runtime. Even though Swift puts a lot of emphasis on static typing, we can get the flexibility to gain more control over types than you might expect.
What is raw value in Swift?
Enumerations in Swift are much more flexible, and don’t have to provide a value for each case of the enumeration. If a value (known as a raw value) is provided for each enumeration case, the value can be a string, a character, or a value of any integer or floating-point type.
What is fast enumeration in Swift?
Fast enumeration is a language feature that allows you to efficiently and safely enumerate over the contents of a collection using a concise syntax.
What is the difference between closure and function in Swift?
Difference between Function and Closure
Function is declared using func keyword whereas Closure doesn’t have func keyword. Function has always name but Closure doesn’t have. Function doesn’t have in keyword but closure has in the keyword.
What is unowned self in Swift?
The most common place you’ll see unowned variables is with closures that declare [unowned self] – this means “I want to reference self inside this closure but I don’t want to own it.” Why unowned rather than weak ? Both would work, but let’s face it: if self is nil inside a closure, something has gone wrong!
What is force unwrapping in Swift?
It’s the action of extracting the value contained inside an Optional . This operation is dangerous because you are telling the compiler: I am sure this Optional value does contain a real value, extract it!
What is difference between any and AnyObject in Swift?
Swift provides two special types for working with nonspecific types: Any can represent an instance of any type at all, including function types. AnyObject can represent an instance of any class type.
What is filter in Swift?
The filter() method returns all the elements from the array that satisfy the provided condition.
How many types of closures are there in Swift?
As shown in the above table, there are three types of closures in Swift, namely global functions, nested functions, and closure expressions. They differ in several aspects, including their use scopes, their names, and whether they capture values, which will be discussed more in a later section.
What is map in Swift?
Swift version: 5.6. The map() method allows us to transform arrays (and indeed any kind of collection) using a transformation closure we specify. The return value will be an array of the same size, containing your transformed elements.
What is safe area in iOS?
Overview. Safe areas help you place your views within the visible portion of the overall interface. UIKit-defined view controllers may position special views on top of your content. For example, a navigation controller displays a navigation bar on top of the underlying view controller’s content.
What is hugging priority in Swift?
The content-hugging priority represents the resistance a view has to grow larger than its intrinsic content size. Conversely, the compression-resistance priority represents the resistance a view has to shrink beyond its intrinsic content size.
What are tuples in Swift?
In Swift, a tuple is a group of different values. And, each value inside a tuple can be of different data types. Suppose we need to store information about the name and price of a product, we can create a tuple with a value to store name (string) and another value to store price (float)
How do I use MVVM in Swift?
You do this with a ViewModel object. First, create a ViewModel object that contains all the necessary data for this ViewController . Go to the ViewModel Xcode project group, which will be empty, create a GameScoreboardEditorViewModel. swift file, and make it a protocol.
What is protocol in Swift?
In Swift, a protocol defines a blueprint of methods or properties that can then be adopted by classes (or any other types). We use the protocol keyword to define a protocol. For example, protocol Greet { // blueprint of a property var name: String { get } // blueprint of a method func message() }
What is a case in Swift?
A switch case is used test variable equality for a list of values, where each value is a case. When the variable is equal to one of the cases, the statements following the case are executed. In Swift, a switch case can contain a temporary let constant, which contains the variable’s value.
How do you pause a loop in Swift?
5 Answers
- Move the loop to a function func playSound(for value: Int, in array: [Int]) { if array.contains(value) { playSound() } }
- Create a timer: Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] _ in guard let array = self?. array, let index = self?. currentIndex else { return } self?.
How do you exit a for loop in Swift?
You can exit a loop at any time using the break keyword. To try this out, let’s start with a regular while loop that counts down for a rocket launch: var countDown = 10 while countDown >= 0 { print(countDown) countDown -= 1 } print(“Blast off!”)
Who controls Swift system?
How is SWIFT governed? SWIFT is a cooperative company under Belgian law and is owned and controlled by its shareholders (financial institutions) representing approximately 2,400 Shareholders from across the world.
What are closures in Swift?
In Swift, a closure is a special type of function without the function name. For example, { print(“Hello World”) } Here, we have created a closure that prints Hello World . Before you learn about closures, make sure to know about Swift Functions.
Which is better MVC or MVVM Swift?
Conclusion. The difference between the MVC and MVVM is View and controller are responsible for calculating the value and assigning the value so the load is more on View and Controller where in MVVM View and Controller are only responsible for assigning the value not calculating the value.
What is RxSwift in iOS?
RxSwift is a library for composing asynchronous and event-based code by using observable sequences and functional style operators, allowing for parameterized execution via schedulers.