Question: Should Delegates Be Weak Or Strong?

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 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 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 a weak variable 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 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 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 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.

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 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.

Is delegate retained?

The delegate object is retained by the receiver. This is a rare exception to the memory management rules described in Advanced Memory Management Programming Guide. An instance of CAAnimation should not be set as a delegate of itself. Doing so (outside of a garbage-collected environment) will cause retain cycles.

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.

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 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 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

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.

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 delegate and datasource in Swift?

A data source is an outlet held by NSView and UIView objects such as table views and outline views that require a source from which to populate their rows of visible data. The data source for a view is usually the same object that acts as its delegate, but it can be any object.