Quick Answer: How Do I Add A Delegate In Swift?

Why is delegate weak in 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 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 datasource in Swift?

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

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 Delegates in 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 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 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 protocols 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.”

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.

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.

What is Table View delegate?

func tableView(UITableView, willDisplay: UITableViewCell, forRowAt: IndexPath) Tells the delegate the table view is about to draw a cell for a particular row.

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 a delegate 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.

How do I create a custom delegate in Objective C?

An Objective-C delegate is an object that has been assigned to the delegate property another object. To create one, you define a class that implements the delegate methods you’re interested in, and mark that class as implementing the delegate protocol.

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 callback in Swift?

In the Swift language you can pass a function as an argument to another function. … The callback function takes two integers as its arguments and returns Void. The callback is called for every element of the given array, with the first argument being the Array index, and the second argument the array element.

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 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.