@resultBuilder attribute in Swift - Mini Project: Build & Apply

Building a Simple HTML Builder with @resultBuilder

📖 Scenario: Imagine you want to create HTML code using Swift in a clean and readable way. Swift's @resultBuilder attribute helps you build complex structures like HTML by writing code that looks like regular Swift code but produces HTML strings.

🎯 Goal: You will build a simple HTML builder using @resultBuilder that lets you write HTML elements in Swift code and get the final HTML string as output.

📋 What You'll Learn

Create a HTMLBuilder result builder to combine strings

Write a function buildHTML that uses @HTMLBuilder

Use the builder to create multiple HTML elements inside buildHTML

Print the final combined HTML string

💡 Why This Matters

🌍 Real World

Using <code>@resultBuilder</code> helps developers write clean and readable code for building complex data like HTML, JSON, or UI layouts.

💼 Career

Understanding <code>@resultBuilder</code> is useful for Swift developers working on SwiftUI, DSLs, or any code that benefits from declarative syntax.

1

Create the HTMLBuilder result builder

Create a struct called HTMLBuilder with the @resultBuilder attribute. Inside it, write a static function buildBlock that takes a variadic parameter of String and returns a single String by joining all parts.

Swift

// Your code here

Need a hint?

Use @resultBuilder before the struct name. The buildBlock function combines all strings into one.

2

Create the buildHTML function using @HTMLBuilder

Write a function called buildHTML that uses the @HTMLBuilder attribute. The function should return a String and have no parameters. Inside the function, return multiple HTML element strings like "

Hello

" and "

Welcome to Swift

" on separate lines.

Swift

@resultBuilder
struct HTMLBuilder {
    static func buildBlock(_ components: String...) -> String {
        components.joined(separator: "\n")
    }
}

// Your code here

Need a hint?

Use @HTMLBuilder before the function. Return multiple strings inside the function body.

3

Call buildHTML and store the result

Create a constant called html and assign it the result of calling buildHTML().

Swift

@resultBuilder
struct HTMLBuilder {
    static func buildBlock(_ components: String...) -> String {
        components.joined(separator: "\n")
    }
}

@HTMLBuilder
func buildHTML() -> String {
    "Hello"
    "Welcome to Swift"
}

// Your code here

Need a hint?

Use let html = buildHTML() to store the result.

4

Print the final HTML string

Write a print statement to display the value of the html constant.

Swift

@resultBuilder
struct HTMLBuilder {
    static func buildBlock(_ components: String...) -> String {
        components.joined(separator: "\n")
    }
}

@HTMLBuilder
func buildHTML() -> String {
    "Hello"
    "Welcome to Swift"
}

let html = buildHTML()

// Your code here

Need a hint?

Use print(html) to show the final HTML string.