Quick Answer: What Is Delegate In Xcode?

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 use protocol and delegate in Swift 4?

Here are the simple steps that you can follow to implement delegates in Objective-C.Create a protocol.Create a delegate property in the class that performs the assigned task.Once the task is complete, it can be used to return the result.Implement the protocol.Nov 9, 2020

What is ARC iOS?

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.

Which method of AppDelegate is called first?

I need to perform some what actions before Main. storyboard is be loaded and the controller will call method viewDidLoad . Now it turns out that method viewDidLoad in controller called before then application:did(will)FinishLaunchingWithOptions in AppDelegate .

What is delegate in iOS with example?

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 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.

Should delegates be weak or strong?

Delegates should always generally be weak.

What is app life cycle in iOS?

During startup, the UIApplicationMain function sets up several key objects and starts the app running. At the heart of every iOS app is the UIApplication object, whose job is to facilitate the interactions between the system and other objects in the app.

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 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 method?

A delegate method is a method that the delegate object is expected to implement. … A delegate is simply a reference to another object and a delegate method is a method of the delegate. A delegate method implements the callback mechanism which usually takes the sender as one of the parameter to be called.

How do I create a custom delegate in Swift?

How To Create A Custom Delegate In SwiftThe Delegate Pattern in Swift.Create A Delegate Protocol.Extend A Delegate Protocol.Implement A Custom Delegate.How To Use A Custom Delegate.Creating Optional Delegate Methods.Jan 3, 2021

What is a delegate in iOS?

Delegation is a simple and powerful pattern in which one object in a program acts on behalf of, or in coordination with, another object. The delegating object keeps a reference to the other object—the delegate—and at the appropriate time sends a message to it.

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).

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.

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 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 the app delegate in xcode?

Overview. Your app delegate object manages your app’s shared behaviors. The app delegate is effectively the root object of your app, and it works in conjunction with UIApplication to manage some interactions with the system.

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.

What is delegate and protocol in IOS?

Protocols are a way to specify a set of methods you want a class to implement if it wants to work with one of your classes. Delegates and Data Sources like UITableViewDelegate and UITableViewDataSource are protocols indeed. … You can also declare some optional methods by declaring them after the @optional specifier.

How do you add a delegate to a scene?

Adding a scene delegate to an existing projectAdd a UIApplicationSceneManifest to the info. plist . … Go to your app delegate and implement application(_:configurationForConnecting:options:) . … Create a new UIResponder subclass called SceneDelegate , let it conform to the UIWindowSceneDelegate and add a window property.Nov 18, 2019