Calculation speed comparing a for-statement with a KVC operation

calculate_avg.swift

import Foundation

class Value: NSObject {
    @objc let raw: Int
    init(_ raw: Int) {
        self.raw = raw
    }

    override var description: String {
        return "\(self.raw)"
    }
}

class Collection: NSObject {
    @objc var values: [Value]
    override init() {
        self.values = []
        super.init()
    }

    override var description: String {
        return "vals: \(self.values)"
    }
}

func makeCollection() -> Collection {
    return Array(0..<100000).map(Value.init).reduce(into: Collection()) { acc, val in
        let temp = acc
        temp.values.append(val)
    }
}

@discardableResult
func testKVC() -> Float {
    let col = makeCollection()
    let avg = col.value(forKeyPath: "[email protected]") as! Float
    return avg
}

@discardableResult 
func testForStatement() -> Float {
    let col = makeCollection()
    var sum: Int = 0
    for val in col.values {
        sum += val.raw
    }
    return Float(sum) / Float(col.values.count)
}

@discardableResult 
func testReduce() -> Float {
    let col = makeCollection()
    let sum = col.values.reduce(0) { acc, value in
        return acc + value.raw
    }
    return Float(sum) / Float(col.values.count)
}

func calculateTime(exec: ()->()) {
    let start = CFAbsoluteTimeGetCurrent()
    exec()
    let end = CFAbsoluteTimeGetCurrent()
    print("calculation time: \(end - start)")
}

calculateTime {
    let r = testKVC() //0.59
    print(r)
}

calculateTime {
    let r = testForStatement() //0.167
    print(r)
}

calculateTime {
    let r = testReduce() //0.167
    print(r)
}