Question: Why Delegates Are Weak IOS?

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 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 retain in iOS?

You send an object a retain message when you want to prevent it from being deallocated until you have finished using it. An object is deallocated automatically when its reference count reaches 0 . retain messages increment the reference count, and release messages decrement it.

What is retain cycle in iOS?

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 are swift delegates?

Delegates are a design pattern that allows one object to send messages to another object when a specific event happens. … Imagine an object A calls an object B to perform an action.

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 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 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 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 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 are delegates in iOS?

Delegate is simply just a means of communication between objects of iOS applications. You can think delegation as a simple way of connecting objects and communicate with each other. In other words we can say that delegate allows one object to send message to other object when any event occurs.

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.

How do you call a delegate in Swift?

Key Steps to DelegationCreate a delegate protocol that defines the messages sent to the delegate.Create a delegate property in the delegating class to keep track of the delegate.Adopt and implement the delegate protocol in the delegate class.Call the delegate from the delegating object.Nov 9, 2015

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 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.

How do I stop retaining cycles in Swift?

We can solve this in two ways. First, we can use [unowned self]: Now the closure doesn’t have a strong reference anymore. Just be careful when using [unowned self] since that, if the object has already been deallocated when the closure is called, a crash will occur.