Question: What Is A Delegate IOS?

What is the difference between delegate and notification in iOS?

A delegate uses protocols and creates a has-a relationship between the two classes.

One of the other benefits of delegates is that you can return something back to the owning class.

Notifications, on the other hand, are more geared towards point to multipoint communication..

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 protocol in Swift with example?

Protocols provide a blueprint for Methods, properties and other requirements functionality. It is just described as a methods or properties skeleton instead of implementation. Methods and properties implementation can further be done by defining classes, functions and enumerations.

What is a retain cycle Swift?

What are retain cycles and memory leaks? 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 delegates in iOS Swift?

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 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 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.

Are delegates type safe?

In essence, a delegate holds a reference to a method and also to the target object on which the method should be called. Delegates in C# are similar to function pointers in C++, but C# delegates are type safe. You can pass methods as parameters to a delegate to allow the delegate to point to the method.

How do you use delegates?

Delegates OverviewDelegates are similar to C++ function pointers, but are type safe.Delegates allow methods to be passed as parameters.Delegates can be used to define callback methods.Delegates can be chained together; for example, multiple methods can be called on a single event.More items…

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!

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 protocol in Swift?

Protocol is a very powerful feature of the Swift programming language. Protocols are used to define a “blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality.” … Write flexible and extensible code in Swift with protocol-oriented programming.

Should delegates be weak or strong?

Delegates should always generally be weak.

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 exactly is a delegate?

A delegate is a person selected to represent a group of people in some political assembly of the United States. … In the United States Congress delegates are elected to represent the interests of a United States territory and its citizens or nationals.

How do delegates work in Swift?

A delegate is an object that acts on behalf of, or in coordination with, another object when that object encounters an event in a program. The delegating object is often a responder object–that is, an object inheriting from NSResponder in AppKit or UIResponder in UIKit–that is responding to a user event.

What is the difference between delegate and protocol 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.

Which statement is true of delegates?

Delegates are type-safe. Delegates serve the same purpose as function pointers in C and pointers to member function operators in C++. E. Only one method can be called using a delegate.