Question: What Is ARC In Swift?

Why is IBOutlet weak?

In Mac development an IBOutlet is usually a weak reference: if you have a subclass of NSViewController only the top-level view will be retained and when you dealloc the controller all its subviews and outlets are freed automatically.

UiViewController use Key Value Coding to set the outlets using strong references..

What is @IBOutlet?

“IBAction” is used by in place of the “return type” void for a method that receives an event sent from Interface Builder. The IBAction keyword allows the programmer to connect the source code to user interface objects in Interface Builder. Neither IBOutlet or IBAction affect how the code is compiled.

Why are delegates weak?

The reason that objects weakly retain their delegates is to avoid retain cycles. Imagine the following scenario: object a creates b and retains it, then sets itself as b ‘s delegate. a is released by its owner, leaving a retain cycle containing a and b . This is actually a very common scenario.

How do I declare an IBOutlet in Swift?

Simplicity rules in swift. If you have a property defined that you want to make accessible to your storyboards, just add the @IBOutlet attribute before your property. Similarly with @IBAction to connect storyboard actions back to code. class MyViewController: UIViewController { @IBOutlet weak var likeButton: UIButton?

What is closure in Swift?

Closures are self-contained blocks of functionality that can be passed around and used in your code. Closures in Swift are similar to blocks in C and Objective-C and to lambdas in other programming languages. … Nested functions are closures that have a name and can capture values from their enclosing function.

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 computed property in Swift?

Swift offers us two kinds of property: a stored property is one that saves a value for use later, and a computed property is one that runs some code in order to calculate the value. … The computed property returns a string based on joining the four stored properties into a sentence.

How do you find the retaining cycle in Swift?

1 Answer. If you are using Xcode 8 or above, you can use the memory graph thingy to see what object holds a reference to what object. Now you can clearly see that it is retained by a closure! That is how you use the memory graph to see where you should put weak-references and avoid retain cycles.

Why we use delegates in Swift?

Delegation is used for everything from handling table view events using UITableViewDelegate , to modifying cache behavior using NSCacheDelegate . The core purpose of the delegate pattern is to allow an object to communicate back to its owner in a decoupled way.

What is strong and weak in Swift?

April 21, 2018. A strong reference means that you want to “own” the object you are referencing with this property/variable. In contrast, with a weak reference you signify that you don’t want to have control over the object’s lifetime.

What is strong reference in Swift?

Strong Reference Cycle. In essence, strong references are used to describe the relationship between objects. When an object has a strong reference to another object, this creates a retain cycle that prevents the object that is being referenced from being deallocated and increases the retain count to 1.

What is retain count in Swift?

Retain Count represents number of owners for a particular object. It is zero till object does not have any owners. Increase in one ownership claim will cause retain count to increase by 1 and decrease will cause it to decrement by 1. Example: – Class A object is created using alloc/init and retain count is 1.

Why delegates are weak in Swift?

With using lazy keyword we are not initializing delegate which means there is no memory leak right now. Let’s break that. Object will be created and there will be memory leak. … Therefore, if the object conforming to the protocol needs to be stored in a weak property then the protocol must be a class-only protocol.

What is atomic and Nonatomic in Swift?

Atomic means only one thread accesses the variable (static type). … Nonatomic means multiple threads access the variable (dynamic type). Nonatomic is thread-unsafe, but it is fast.

What is lazy property in Swift?

Lazy Stored Properties. A lazy stored property is a property whose initial value isn’t calculated until the first time it’s used. … You must always declare a lazy property as a variable (with the var keyword), because its initial value might not be retrieved until after instance initialization completes.

What is a weak VAR in Swift?

A weak reference is just a pointer to an object that doesn’t protect the object from being deallocated by ARC. … In Swift, all weak references are non-constant Optionals (think var vs. let ) because the reference can and will be mutated to nil when there is no longer anything holding a strong reference to it.

Why Swift is protocol oriented programming?

Swift checks for protocol conformity issues at compile-time, allowing developers to discover some fatal bugs in the code even before running the program. Protocols allow developers to write flexible and extensible code in Swift without having to compromise the language’s expressiveness.

How do you fix a swift memory leak?

How to eliminate Memory Leaks?Don’t create them. Have a strong understanding of memory management. … Use Swift Lint. It is a great tool that enforces you to adhere to a code style and keep rule 1. … Detect leaks at run-time and make them visible. … Profile the app frequently. … Unit Test Leaks with SpecLeaks.May 7, 2018

Does Swift have garbage collection?

Swift uses a simple garbage collection mechanism. It’s called ARC (Automatic Reference Counting). This approach is based on tracking the strong references count to an object held by other objects.