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struct Nucleotide {
private let validNucleotides = "ATCG"
private var errorMessage: ((Character) -> (String)) = { n in
return "\(n) is not a valid Nucleotide"
}
let dna: String
init(_ dna: String) {
self.dna = dna
}
}
extension Nucleotide {
func complementOfDNA() throws -> String {
var sequence: String = ""
try dna.forEach { n in
if !validNucleotides.contains(n) {
throw TranscriptionError.invalidNucleotide("\(n) is not a valid Nucleotide")
}
if n == "G" {
sequence += "C"
} else if n == "C" {
sequence += "G"
} else if n == "T" {
sequence += "A"
} else if n == "A" {
sequence += "U"
}
}
return sequence
}
}
// Refactor to switch and improve error handling
extension Nucleotide {
func complementOfDNA() throws -> String {
var sequence: String = ""
try dna.forEach { n in
switch n {
case "G":
sequence += "C"
case "C":
sequence += "G"
case "T":
sequence += "A"
case "A":
sequence += "U"
default:
throw TranscriptionError.invalidNucleotide(errorMessage(n))
}
}
return sequence
}
}
// using map to reduce code
extension Nucleotide {
func complementOfDNA() throws -> String {
return try dna.map { (n) -> String in
switch String(n) {
case "G": return "C"
case "C": return "G"
case "T": return "A"
case "A": return "U"
default:
throw TranscriptionError.invalidNucleotide(errorMessage(n))
}
}.joined()
}
}
// with map and enum
extension Nucleotide {
func complementOfDNA() throws -> String {
return try dna.map { (n) -> String in
if let t = nucleotide(rawValue: n)?.transcribe() {
return t
} else {
throw TranscriptionError.invalidNucleotide(errorMessage(n))
}
}.joined()
}
}
extension Nucleotide {
private enum nucleotide: Character {
case A = "A"
case T = "T"
case G = "G"
case C = "C"
func transcribe() -> String? {
switch self {
case .A: return "U"
case .T: return "A"
case .G: return "C"
case .C: return "G"
}
}
}
}
enum TranscriptionError: LocalizedError {
case invalidNucleotide(_ n: String)
}
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