What Is Weak Self In Swift?

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..

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.

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 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 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.

What is the difference between weak and unowned?

The first difference you need to know about is that an unowned reference is always expected to have a value. … When that happens, the reference is set to nil . Because a weak reference can be set to nil , it is always declared as an optional. That is the second difference between weak and unowned references.

What is strong what is weak why we want to use unowned and weak self?

In Swift, we need to use weak self and unowned self to give ARC the required information between relationships in our code. Without using weak or unowned you’re basically telling ARC that a certain “strong reference” is needed and you’re preventing the reference count from going to zero.

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.

What is weak 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 outlets are weak Swift?

Because the outlet is declared weak, it is automatically set to nil when it’s deallocated. Because the outlet is an implicitly unwrapped optional, it has no value, that is, is equal to nil , and the application would crash as a result. If this happens, chances are you’re doing something you shouldn’t be doing.

What is optional in Swift?

An optional in Swift is basically a constant or variable that can hold a value OR no value. The value can or cannot be nil. It is denoted by appending a “?” after the type declaration. … This is a big impact on the language Swift itself because what that means is that anything non-optional types can never be nil.

Why is delegate weak in iOS?

For delegation patters in iOS, the delegated object is the parent, because there is no need for the delegate caller to exist without the delegated object. … When you define a delegate object as property, it’s used a weak reference in the object it is defined in(lets say A, i.e. the delegate object is a property of A).

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 and weak in iOS?

strong is the default. An object remains “alive” as long as there is a strong pointer to it. weak specifies a reference that does not keep the referenced object alive. A weak reference is set to nil when there are no strong references to the object.

Why we use lazy VAR in Swift?

Swift has a mechanism built right into the language that enables just-in-time calculation of expensive work, and it is called a lazy variable. These variables are created using a function you specify only when that variable is first requested. … The lazy property is marked as lazy var .

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 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.

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 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 lazy 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 generic in Swift?

Generic code enables you to write flexible, reusable functions and types that can work with any type, subject to requirements that you define. … Generics are one of the most powerful features of Swift, and much of the Swift standard library is built with generic code.