Compare version numbers for the format MAJOR.MINOR.REVISION in Swift

VersionNumber.swift

public struct VersionNumber: Equatable, Comparable {
  public let version: String

  public init(version: String) {
    self.version = version
  }
}

// Returns 1 if lhs > rhs, -1 if lhs < rhs and 0 if lhs = rhs
private func compare(_ lhs: VersionNumber, _ rhs: VersionNumber) -> Int {
  let lhsVersionComponents = lhs.version.components(separatedBy: ".").map { Int($0) ?? 0 }
  let rhsVersionComponents = rhs.version.components(separatedBy: ".").map { Int($0) ?? 0 }

  for i in 0..<max(lhsVersionComponents.count, rhsVersionComponents.count) {
    let l = i >= lhsVersionComponents.count ? 0 : lhsVersionComponents[i]
    let r = i >= rhsVersionComponents.count ? 0 : rhsVersionComponents[i]
    let comparison = l - r
    if comparison > 0 {
      return 1
    } else if comparison < 0 {
      return -1
    } // (else test next component)
  }

  return 0 // version numbers are equal
}

public func > (lhs: VersionNumber, rhs: VersionNumber) -> Bool {
  return compare(lhs, rhs) == 1
}

public func < (lhs: VersionNumber, rhs: VersionNumber) -> Bool {
  return compare(lhs, rhs) == -1
}

public func == (lhs: VersionNumber, rhs: VersionNumber) -> Bool {
  return compare(lhs, rhs) == 0
}