Swift Language Patterns

Swift Language Patterns

Apply current Swift language syntax without changing behavior or evaluation order. Route deep decoding to swift-codable, formatting to swift-formatstyle, naming to swift-api-design-guidelines, concurrency to swift-concurrency, and SwiftUI state/view work to swiftui-patterns.

Contents

• If/Switch Expressions
• Typed Throws
• Result Builders
• Property Wrappers
• Opaque and Existential Types
• Guard Patterns
• Never Type
• Regex Builders
• Codable Best Practices
• Modern Collection APIs
• FormatStyle
• String Interpolation
• Common Mistakes
• Review Checklist
• References

If/Switch Expressions

For modernization, pin current behavior and evaluation order, make one semantic rewrite, compile the affected module, and run focused fixtures/tests. Fix any change before continuing; repeat until behavior is preserved.

Swift 5.9+ allows if and switch as expressions that return values. Use them to assign, return, or initialize directly.

// Assign from if expression
let icon = if isComplete { "checkmark.circle.fill" } else { "circle" }

// Assign from switch expression
let label = switch status {