Swift Typealias

Swift Typealias: In this tutorial, you will learn about typealias and its use cases in Swift.

A typealias in Swift is literally an alias for an existing type. Simple, isn’t it? They can be useful in making your code somewhat more readable. By using them in a brilliant manner they can be really useful in your codebase.

A type alias allows you to give a new name to an existing data type into your program. After a type alias is declared, the aliased name can be used rather than the existing sort all through the program.

Type alias don’t create new sorts. They essentially give a new name to a current type.

The main purpose typealias is to make our code more readable, and clearer in setting for human arrangement.

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How to create a typealias?

It is declared using the watchword typealias as:

typealias name = existing type

In Swift, you can use typealias for most types. They can be either:

• Built-in types (for.eg: String, Int)

• User-defined types (for.e.g: class, struct, enum)

• Complex types (for e.g: closures)

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Typealias for built-in types

You can use typealias for all built in data Types as String, Int, Float and so forth

For instance:

typealias StudentName = String

The above declaration allows StudentName to be used wherever as opposed to String. In this way, on the off chance that you need to create a constant of type string but addresses more like student name. You can do as:

let name:StudentName = "Salman"

Without using typealias, you ought to declare consistent of type string as:

let name:String = "Salman"

Above the two examples creates a constant of type String. But, declaring with typealias, our code turns out to be more readable.

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Typealias for user defined types

There are numerous situations when you need to create your own data type. Assume you need to create a Type that addresses Student, you can create it using a class as:

class Student {

}

Presently a group of students can be addressed as an array as:

var students:Array<Student> = []

The above declaration can be made more readable by creating your own sort for Array<student> using typealias as:

typealias Students = Array<Student>

Presently we can make our code more readable as:

var students:Students = []

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Typealias for complex types

Lets examine one more example. Assume we have a technique that takes a closure as an input parameter.

Try not to stress in the event that you don’t think about closures. Simply consider it as a special type of function. We have clarified it detail in the tutorial: Swift closures.

func someMethod(oncomp:(Int)->(String)){

}

The above example takes a closure as an input to someMethod. The closure takes an Int value and returns string.

You can see the use of (Int)- >(String) makes less sense to the reader. You can use typealias to provide a new name for it:

typealias CompletionHandler = (Int)->(String)

Presently you can change the strategy as:

func someMethod(oncomp:CompletionHandler){

}

We can see a similar code looks all the more clear and programmer friendly with the us of typealias.

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