BuildOptional and buildEither in Swift - Mini Project: Build & Apply

Using BuildOptional and BuildEither in Swift

📖 Scenario: You are creating a simple Swift function that builds a message based on optional and conditional values.

🎯 Goal: Build a Swift function that uses BuildOptional and BuildEither to conditionally create parts of a message.

📋 What You'll Learn

Create an optional string variable called optionalPart with the value "Optional part included."

Create a boolean variable called includeFirst set to true

Use BuildOptional to include optionalPart only if it is not nil

Use BuildEither to choose between two strings based on includeFirst

Print the final combined message

💡 Why This Matters

🌍 Real World

Result builders like <code>BuildOptional</code> and <code>BuildEither</code> help Swift developers write clean, readable code for building UI views, DSLs, or complex strings with conditional parts.

💼 Career

Understanding these concepts is useful for Swift developers working on SwiftUI apps or any code that benefits from declarative and conditional building patterns.

1

Create the optional string variable

Create an optional string variable called optionalPart and set it to "Optional part included."

Swift

# Create the optional string variable 'optionalPart'
# Your code here

Need a hint?

Use let optionalPart: String? = "Optional part included." to create the optional string.

2

Create the boolean variable

Create a boolean variable called includeFirst and set it to true

Swift

let optionalPart: String? = "Optional part included."
# Create the boolean variable 'includeFirst'
# Your code here

Need a hint?

Use let includeFirst: Bool = true to create the boolean variable.

3

Use BuildOptional and BuildEither to build message parts

Use BuildOptional to include optionalPart only if it is not nil, and use BuildEither to choose between "First part included." and "Second part included." based on includeFirst. Store the combined message in a variable called message.

Swift

let optionalPart: String? = "Optional part included."
let includeFirst: Bool = true
# Use BuildOptional and BuildEither to build the message
# Your code here

Need a hint?

Define a @resultBuilder called MessageBuilder with buildOptional and buildEither methods. Use it in buildMessage() to conditionally add parts.

4

Print the final message

Write a print statement to display the variable message

Swift

let optionalPart: String? = "Optional part included."
let includeFirst: Bool = true

@resultBuilder
struct MessageBuilder {
    static func buildBlock(_ components: String...) -> String {
        components.joined(separator: " ")
    }
    static func buildOptional(_ component: String?) -> String {
        component ?? ""
    }
    static func buildEither(first component: String) -> String {
        component
    }
    static func buildEither(second component: String) -> String {
        component
    }
}

@MessageBuilder
func buildMessage() -> String {
    if includeFirst {
        "First part included."
    } else {
        "Second part included."
    }
    optionalPart
}

let message = buildMessage()
# Print the message
# Your code here

Need a hint?

Use print(message) to display the final combined message.