Comparing version strings

VersionsComparison.playground

import UIKit
import Foundation

func compareVersions(version1: String, version2: String) -> ComparisonResult {
	let version1Components = version1.components(separatedBy: ".")
	let version2Components = version2.components(separatedBy: ".")
	
	let length = max(version1Components.count, version2Components.count)
	
	for i in 0 ..< length {
		let version1Component: Int
		let version2Component: Int
		
		if i < version1Components.count {
			version1Component = Int(version1Components[i]) ?? 0
		} else {
			version1Component = 0
		}
		if i < version2Components.count {
			version2Component = Int(version2Components[i]) ?? 0
		} else {
			version2Component = 0
		}
		
		guard version1Component != version2Component else { continue }
		
		return version1Component < version2Component ? .orderedAscending : .orderedDescending
	}
	
	return .orderedSame
}

func performCustomAndStringVersionComparisons(version1: String, version2: String) -> (String, String) {
	let comparison = compareVersions(version1: version1, version2: version2)
	let comparisonDescription = getComparisonDescription(comparison: comparison)
	
	let numericStringComparison = version1.compare(version2, options: .numeric)
	let numericStringComparisonDescription = getComparisonDescription(comparison: numericStringComparison)
	
	return (comparisonDescription, numericStringComparisonDescription)
}

func getComparisonDescription(comparison: ComparisonResult) -> String {
	switch comparison {
	case .orderedSame:
		return "Same"
	case .orderedAscending:
		return "Lower"
	case .orderedDescending:
		return "Greater"
	}
}


let comparisonWhenDifferent = performCustomAndStringVersionComparisons(version1: "1.0.1", version2: "1.0.3")
let comparisonWhenSame = performCustomAndStringVersionComparisons(version1: "1.0", version2: "1.0")
let comparisonWhenShouldBeSame1 = performCustomAndStringVersionComparisons(version1: "1.0", version2: "1.0.0")
let comparisonWhenShouldBeSame2 = performCustomAndStringVersionComparisons(version1: "1.0.0", version2: "1.0")