Performance Optimization in Swift

Introduction

This guide covers techniques and best practices for optimizing Swift code performance, from basic optimizations to advanced memory management strategies.

Memory Management

Value Types vs Reference Types

// Value type (Stack allocation)
struct Point {
    var x: Double
    var y: Double
}

// Reference type (Heap allocation)
class Circle {
    var center: Point
    var radius: Double

    init(center: Point, radius: Double) {
        self.center = center
        self.radius = radius
    }
}

Compiler Optimizations

Build Settings

• Whole Module Optimization
• Link Time Optimization
• Optimization Level (-O, -Osize)

// Enable optimizations in code
@inline(__always) func performCalculation(_ value: Double) -> Double {
    return value * 2.0
}

// Avoid dynamic dispatch
@objc final class OptimizedClass: NSObject {
    func fastMethod() {
        // Implementation
    }
}

Collection Performance

Choosing the Right Collection

// Array: O(1) append, O(n) insert/remove
var array = [1, 2, 3]

// Set: O(1) lookup, insert, remove
var set = Set([1, 2, 3])

// Dictionary: O(1) lookup, insert, remove
var dict = ["key": "value"]

// ContiguousArray for better performance with value types
var contiguousArray = ContiguousArray([1, 2, 3])

Lazy Evaluation

Lazy Properties and Sequences

// Lazy property
class DataProcessor {
    lazy var expensiveResult: [Int] = {
        return performExpensiveOperation()
    }()

    // Lazy sequence
    let numbers = Array(1...1000)
    let processed = numbers.lazy
        .map { $0 * 2 }
        .filter { $0 > 100 }
}

Memory Layout

Struct Memory Alignment

// Poor memory layout
struct Inefficient {
    let byte: Int8
    let int: Int64
    let flag: Bool
}

// Optimized memory layout
struct Efficient {
    let int: Int64
    let byte: Int8
    let flag: Bool
}

Profiling Tools

Using Instruments

1. Time Profiler
2. Allocations
3. Leaks
4. System Trace

Best Practices

1. Use value types when appropriate
2. Minimize heap allocations
3. Avoid unnecessary string operations
4. Cache expensive computations
5. Profile before optimizing

Common Optimizations

String Optimization

// Inefficient string concatenation
var result = ""
for i in 1...1000 {
    result += "\(i),"
}

// Optimized approach
var components: [String] = []
components.reserveCapacity(1000)
for i in 1...1000 {
    components.append("\(i)")
}
let result = components.joined(separator: ",")

Batch Operations

// Efficient batch updates
UIView.performWithoutAnimation {
    view1.alpha = 0
    view2.transform = .identity
    view3.frame = newFrame
}

Next Steps

1. Explore Security
2. Review Testing and Debugging
3. Study Package Management