What Is Strong What Is Weak Why We Want To Use Unowned And Weak Self?

What is weak self in Swift?

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 lazy VAR?

A lazy var is a property whose initial value is not calculated until the first time it’s called. It’s part of a family of properties in which we have constant properties, computed properties, and mutable properties.

What is capture list in Swift?

Swift lets us specify a capture list to determine how values used inside the closure should be captured. The most common alternative to strong capturing is called weak capturing, and it changes two things: Weakly captured values aren’t kept alive by the closure, so they might be destroyed and be set to nil .

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 outlets are weak in Swift?

weak is used because in most situations the owner of the outlet isn’t the same as the owner of the view. For example, a view controller doesn’t own someLabel – the view controller’s view does. var because outlets are, by definition, set after initialization.

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.

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 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 a weak VAR?

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.

What is the difference between weak and strong?

A variable that does not take ownership of an object is known as a weak reference. strong is the default. An object remains “alive” as long as there is a strong pointer to it. … A weak reference is set to nil when there are no strong references to the object.

What is a 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.

What is ARC in Swift?

Swift uses Automatic Reference Counting (ARC) to track and manage your app’s memory usage. … ARC automatically frees up the memory used by class instances when those instances are no longer needed.

What is $0 and $1 in Swift?

$0 and $1 are Closure’s first and second shorthand arguments (a.k.a. Shorthand Argument Names or SAN for short). The shorthand argument names are automatically provided by Swift. The first argument can be referenced by $0 , the second argument can be referenced by $1 , the third one by $2 , and so on.

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 are strong and weak references?

Strong References: This is the default type/class of Reference Object. Any object which has an active strong reference are not eligible for garbage collection. … Weak References: Weak Reference Objects are not the default type/class of Reference Object and they should be explicitly specified while using them.

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.

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 the difference between closure and function in Swift?

Roughly, a closure is a block of code that may capture variable values from its surrounding scope. … In Swift, a function (including a method) is semantically just a closure with a static name — you can pass a function name anywhere that a closure parameter is required, assuming that the type signature is correct.