Swift’s Result Builders

TupleViews and more!

Photo by Clem Onojeghuo on Unsplash

Difficulty: Beginner | Easy | Normal | Challenging

This article has been developed using Xcode 14.2, and Swift 5.7.2

Prerequisites:

You need to be able to code in Swift, perhaps using Playgrounds and be able to use SwiftUI

Terminology

@resultBuilder: An attribute that transforms a sequence of statements into a single combined value

TupleView: A View created from a swift tuple of View values

Tuple: A group of zero or more values represented as a single compound value

Type: A representation of the type of data that can be processed, for example Integer or String

Variadric parameters: A parameter for a function that accepts zero or more values of the specified type

Result builders: The prerequisites

We need to understand a number of things to be able to fully understand

Tuples…from the beginning

I’ve already written about Tuples in a previous article as they allow you to store multiple values in a single variable.

Something like var person = (“Steve”, 22) will do it in code. As you can see two elements are stored in the property called person.

TupleView (represents a view)

A TupleView is a concrete SwiftUI View type that stores multiple View.

It is used internally by SwiftUI when combining views but developers typically do not interact with this type directly.

However you *can* use a TupleView and you might create a ContentView that shows the Words “Hello” and “World” on two different lines as they are contained within a VStack.

struct ContentView: View {
    var body: some View {
        VStack {
            TupleView((Text("Hello"),Text("World")))
        }
    }
}

A look at VStack

We can use TupleView and @resultBuilder to look at VStack (and how similar views) work under the hood. This also gives a first opportunity to look at result…