← Back to Swift Course | Chapter 14: Standard Library & Best Practices | Lesson 7 of 7

Swift Best Practices

Best practices are the tried-and-true habits experienced Swift developers follow to write code that's clean, safe, and easy for others to read.

In this page:

  1. Prefer let and Value Types
  2. Avoid Force Unwrapping
  3. Write Self-Documenting Code

Prefer let and Value Types

Defaulting to let and structs produces code that's easier to reason about, since values can't unexpectedly change from elsewhere in the program.

Example: Prefer let and Value Types

markup 
// Define a struct `Point`
struct Point {
    let x: Int
    let y: Int
}
// Declare a constant `origin`, set to `Point(x: 0, y: 0)`
let origin = Point(x: 0, y: 0)
// Print "Origin: (\(origin.x), \(origin.y))" to the console
print("Origin: (\(origin.x), \(origin.y))")

Avoid Force Unwrapping

Using if let, guard let, or ?? instead of ! avoids crashes when a value turns out to be missing, making code more resilient.

Example: Avoid Force Unwrapping

markup 
// Define the function `safeDivide` taking `a`, `b` and returning a `Int?`
func safeDivide(_ a: Int, by b: Int) -> Int? {
    guard b != 0 else { return nil }
    // Return `a / b` from this function
    return a / b
}
// Declare a constant `result`, set to `safeDivide(10, by: 0) ?? 0`
let result = safeDivide(10, by: 0) ?? 0
// Print "Safe result: \(result)" to the console
print("Safe result: \(result)")

Write Self-Documenting Code

Descriptive names for functions, parameters, and variables make code readable without needing extra comments to explain what it does.

Example: Write Self-Documenting Code

markup 
// Define the function `calculateTotalPrice` taking `itemPrice`, `quantity`, `taxRate` and returning a Double
func calculateTotalPrice(itemPrice: Double, quantity: Int, taxRate: Double) -> Double {
    // Declare a constant `subtotal`, set to `itemPrice * Double(quantity)`
    let subtotal = itemPrice * Double(quantity)
    // Return `subtotal + (subtotal * taxRate)` from this function
    return subtotal + (subtotal * taxRate)
}
// Print `calculateTotalPrice(itemPrice: 20.0, quantity: 3, taxRate: 0.08)` to the console
print(calculateTotalPrice(itemPrice: 20.0, quantity: 3, taxRate: 0.08))
Related Topics

Combine Basics · Swift Package Manager · FileManager Basics · Codable and JSON

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Common Mistakes
  1. Defaulting to class and force-unwrapping everywhere out of habit, instead of preferring struct, let, and safe optional handling by default.
  2. Writing overly clever one-liners that sacrifice readability, when Swift's clarity-focused design favors explicit, self-documenting code.
  3. Ignoring compiler warnings (like suggesting let over var) instead of treating them as free code-quality guidance.
Chapter Summary
  • Prefer let over var, and structs over classes, unless mutability or reference semantics are specifically needed.
  • Avoid force-unwrapping (!) except where a nil value would represent a genuine programming error.
  • Use clear, descriptive names and let Swift's type inference reduce noise without sacrificing clarity.
  • Lean on the compiler: address warnings, use guard for early exits, and let strong typing catch bugs early.
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