In the Swift programming language, the word typealias is an expression that allows a type to be defined by a different name. This can be used to shorten the length of a type’s name or to give it a more meaningful name.
A simple example for using typealias:
typealias Point = (x: Int, y: Int)
In this example, we renamed a type (x: Int, y: Int) to the name Point. Now we can use this customized Point type:
func distance(from point1: Point, to point2: Point) -> Double {
let dx = Double(point1.x - point2.x)
let dy = Double(point1.y - point2.y)
return sqrt(dx*dx + dy*dy)
}
Here we wrote a function that calculates the distance between two points using the Point type.
typealias can also be used to make complex type definitions more meaningful and readable. For example:
typealias CompletionHandler<T> = (Result<T, Error>) -> Void
In this example, we have defined a CompletionHandler type, this type is used to call a function that returns a Result type, and if an error of type Error occurs, it will catch and handle it. By using this customized type, we can more meaningfully handle the results returned by the functions.
