Swift forEach vs map vs for-in performance test

foreach-vs-map-vs-forin-performance-test.swift

/// measure calls a block for a specified number of iterations and returns the execution time in seconds
func measure(name: String = "", iterations: Int = 10, forBlock block: () -> Void) -> Double {
    let startDate = Date()
    
    for _ in 0..<iterations {
        block()
    }
    
    let endDate = Date()
    let timeInterval: Double = endDate.timeIntervalSince(startDate)
    print("\(name):\t \(timeInterval) seconds")
    return timeInterval
}

/// Test data
func createUUIDs() -> [UUID] {
    return Array(repeating: UUID(), count: 1000)
}

/// Performance tests
let input = createUUIDs()
measure(name: "forEach", iterations: 1, forBlock: {
    var outputA = [String]()
    input.forEach({ outputA.append($0.description) })
})

measure(name: "map", iterations: 1, forBlock: {
    let outputB = input.map({ $0.description })
})


measure(name: "for-in", iterations: 1, forBlock: {
    var outputC = [String]()
    for i in input {
        outputC.append(i.description)
    }
})