Quick Answer: How Do I Use Protocol And Delegate In Swift 4?

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 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 protocol and delegate in Swift?

Delegation can be used to respond to a particular action, or to retrieve data from an external source without needing to know the underlying type of that source. Apple notes that: A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality.

How do you call a protocol in Swift?

First, we add @objc keyword in front of the protocol keyword. Then we add the @objc optional keyword in front of our optional method/variable. When you use a method or property in an optional requirement, its type automatically becomes an optional.

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.

Can Swift protocols have properties?

A protocol can require any conforming type to provide an instance property or type property with a particular name and type. The protocol doesn’t specify whether the property should be a stored property or a computed property—it only specifies the required property name and type.

What is use of 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.”

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

How do I use delegates in Swift?

The basic steps to use delegation are the same for both Objective-C and Swift:Create 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.More items…•Nov 9, 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.

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 does delegate mean 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.

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 you use protocols?

A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality. The protocol can then be adopted by a class, structure, or enumeration to provide an actual implementation of those requirements.

What is generic in Swift?

Generic code enables you to write flexible, reusable functions and types that can work with any type, subject to requirements that you define. … Generics are one of the most powerful features of Swift, and much of the Swift standard library is built with generic code.

What is a protocol in Objective C?

Objective-C allows you to define protocols, which declare the methods expected to be used for a particular situation. Protocols are implemented in the classes conforming to the protocol. … We have a delegate object that holds the reference of the calling object that implements the 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.

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 enum in Swift?

An enumeration defines a common type for a group of related values and enables you to work with those values in a type-safe way within your code. Enumerations in Swift are first-class types in their own right. …

How do you delegate in Objective C?

Objective C Delegation by ExampleCreate a protocol.Create a delegate property in the class that performs the assigned task.Once the task is complete, delegate property to be used to return the result.Implement the protocol.