What Are Delegates In IOS Swift?

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 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 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 datasource in Swift?

The object that acts as the data source of the table view. Availability.

What is UITableViewDelegate?

UITableViewDelegate is a protocol you implement on your class to receive UITableView events. … The UITableViewDelegate protocol declares a method that the delegate must implement to return a cell object that the table view uses when drawing a particular row.

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 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 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 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.

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.

What are the methods of delegation?

Put these seven delegation strategies into practice and watch as your organization’s efficiency increases:Learn to let go. … Establish a firm priority system. … Play to your workers’ strengths. … Always include instructions. … Don’t be afraid to teach new skills. … Trust, but verify.More items…•May 7, 2015

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 are delegates and protocols in iOS?

Delegates are a use of the language feature of protocols. The delegation design pattern is a way of designing your code to use protocols where necessary. In the Cocoa frameworks, the delegate design pattern is used to specify an instance of a class which conforms to a particular protocol.

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 data source in Swift?

To manage the data, you provide the table with a data source object—that is, an object that implements the UITableViewDataSource protocol. A data source object responds to data-related requests from the table. It also manages the table’s data directly, or coordinates with other parts of your app to manage that data.

What is delegate in xcode?

A delegate is an object that another class can pass messages to. … Delegate protocols exist so that you can make sure that the delegate object has the necessary methods to deal with your messages. Methods in a delegate protocol can be @optional or enforced. Any methods that are optional don’t have to be defined.

Should delegates be weak or strong?

Delegates should always generally be weak.