Quick Answer: Why Is IBOutlet Weak?

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..

What is difference between weak and strong in Swift?

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. A weak reference is like observing the tree from afar. …

How do you declare an IBOutlet property?

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 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.

Why we use lazy in Swift?

Lazy properties are also useful when the initial value for a property requires complex or computationally expensive setup that shouldn’t be performed unless or until it’s needed. The example below uses a lazy stored property to avoid unnecessary initialization of a complex class.

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.

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 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 the difference between strong and weak?

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 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 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.

Should delegates be weak or strong?

Delegates should always generally be weak.

What is difference between protocol and delegate in Swift?

Protocol is a set of methods (either optional or required) that would be implemented by the class which conforms to that protocol. While, delegate is the reference to that class which conforms to that protocol and will adhere to implement methods defined in protocol. Have a look at this Apple doc for more detail.

What is IB in IBOutlet?

IB stands for interface builder, as you connect objects via the interface builder .

What is difference between delegate and datasource in iOS?

A data source is almost identical to a delegate. The difference is in the relationship with the delegating object. Instead of being delegated control of the user interface, a data source is delegated control of data.

What is IBOutlet and IBAction in Swift?

@IBAction is similar to @IBOutlet , but goes the other way: @IBOutlet is a way of connecting code to storyboard layouts, and @IBAction is a way of making storyboard layouts trigger code. This method takes one parameter, called sender . It’s of type UIButton because we know that’s what will be calling the method.

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.

Why delegates are weak 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 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 memory leak in Swift?

A memory leak in iOS is when an amount of allocated space in memory cannot be deallocated due to retain cycles. Since Swift uses Automatic Reference Counting (ARC), a retain cycle occurs when two or more objects hold strong references to each other.

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.