swift

Swift: Idiomatic Efficiency Reference

When to Use

• Use this skill when the task matches this description: Language-specific super-code guidelines for swift.

Table of Contents

1. [Optionals](#optionals)
2. [Collections & Functional Transforms](#collections)
3. [Value vs Reference Types](#value-types)
4. [Error Handling](#errors)
5. [Concurrency](#concurrency)
6. [Protocol-Oriented Design](#protocols)
7. [Anti-patterns specific to Swift](#antipatterns)

---

1. Optionals {#optionals}

// ❌ Force unwrap
let name = user.name!

// ✅ — guard or if-let
guard let name = user.name else { return }

// ❌ Nested if-let pyramid
if let user = fetchUser() {
    if let address = user.address {
        if let city = address.city {
            display(city)
        }
    }
}

// ✅ — chained optional binding
if let city = fetchUser()?.address?.city {
    display(city)
}
// or guard-let for early exit
guard let city = fetchUser()?.address?.city else { return }
display(city)

// ❌ Ternary for default
let name = user.name != nil ? user.name! : "Unknown"

// ✅
let name = user.name ?? "Unknown"

// ❌ Optional map when if-let is clearer for side effects
user.name.map { display($0) }

// ✅ — map for transforms, if-let for side effects
let upper = user.name.map { $0.uppercased() }
if let name = user.name { display(name) }

---

2. Colle