Converting string to Bool and testing for IF statement in Swift - swift

Question

So I am trying to take thee first index of a string (fullName) and test it to see if it matches all vowels lower and uppercased... for some reason when I use the .startIndex I test one letter at a time with a If statement.
Ia there a way to test all vowels at once ()I tried || in between each and it gave me the error "cannot convert string to Bool". Appreciate any help.
func lyricsForName(lyricsTemplate: String, fullName: String) -> String {
let shortName = shortNameFromName(name: fullName)
let index = fullName[fullName.startIndex]
if index== ("a","A"){
let lyrics = lyricsTemplate
.replacingOccurrences(of:"<FULL_NAME>", with: fullName)
.replacingOccurrences (of:"<SHORT_NAME>", with: fullName )
return lyrics
}else{
let lyrics = lyricsTemplate
.replacingOccurrences(of:"<FULL_NAME>", with: fullName)
.replacingOccurrences (of:"<SHORT_NAME>", with: shortName )
return lyrics

Answer 1

You can do it as previously answered, but this is a more Swifty way using the available APIs:
extension String {
var firstThreeLettersAreVowels: Bool {
guard characters.count >= 3 else {
return false
}
let firstThreeLetters = substring(to: index(startIndex, offsetBy: 3))
let isAllVowels = CharacterSet(charactersIn: firstThreeLetters).isSubset(of: CharacterSet.vowels)
return isAllVowels
}
var isLower: Bool {
return CharacterSet(charactersIn: self).isSubset(of: CharacterSet.lowercaseLetters)
}
var isUpper: Bool {
return CharacterSet(charactersIn: self).isDisjoint(with: CharacterSet.lowercaseLetters)
}
}
extension CharacterSet {
static var vowels: CharacterSet {
return CharacterSet(charactersIn: "AEIOUYaeiouy")
}
}
Or the one liner (without length check) is
extension String {
var firstThreeLettersAreVowels: Bool {
return CharacterSet(charactersIn: substring(to: index(startIndex, offsetBy: 3)))
.isSubset(of: CharacterSet(charactersIn: "AEIOUYaeiouy"))
}
}
This allows you rely on existing APIs rather than trying to do the work yourself, and it should be pretty fast.

Answer 2

Here is one way to do it. You can use an array of vowels and then test if the array contains the first character:
let fullName = "Albert"
let vowels = "aeiouAEIOU".characters
if let first = fullName.characters.first, vowels.contains(first) {
print("\(fullName) starts with a vowel")
}
Albert starts with a vowel
Note: Using fullName.characters.first is safer than fullName[fullName.startIndex] because the latter will crash for an empty String.

Answer 3

all kudos please to PEEJWEEJ answer
the characterset was his idea :)
i made it only more general
import Foundation
extension String {
func isFirstLetters(count: Int, of characterSet: CharacterSet) -> Bool {
guard characters.count >= count else {
return false
}
let firstLetters = substring(to: index(startIndex, offsetBy: count))
let isInSubset = CharacterSet(charactersIn: firstLetters).isSubset(of: characterSet
)
return isInSubset
}
}
extension CharacterSet {
static var vowels: CharacterSet {
return CharacterSet(charactersIn: "AEIOUYaeiouy")
}
}
some Test cases:
"abcDEf".isFirstLetters(count: 3, of: .vowels) // false
"aioDEf".isFirstLetters(count: 3, of: .vowels) // true
"abcDEf".isFirstLetters(count: 1, of: .vowels) // true
"bbcDEf".isFirstLetters(count: 1, of: .vowels) // false
"ibcDEf".isFirstLetters(count: 1, of: .vowels) // true
"ABcdef".isFirstLetters(count: 3, of: .uppercaseLetters) // false
"ABDdef".isFirstLetters(count: 3, of: .uppercaseLetters) // true
"abBABcdef".isFirstLetters(count: 3, of: .lowercaseLetters) // false
"abbABDdef".isFirstLetters(count: 3, of: .lowercaseLetters) // true
"ABD".isFirstLetters(count: 3, of: CharacterSet(charactersIn: "A"..."C")) // false
"ABD".isFirstLetters(count: 3, of: CharacterSet(charactersIn: "A"..."D")) // true
debug info:
extension CharacterSet {
var characters: [Character] {
var result: [Character] = []
for plane: UInt8 in 0...16 where self.hasMember(inPlane: plane) {
for unicode in UInt32(plane) << 16 ..< UInt32(plane + 1) << 16 {
if let uniChar = UnicodeScalar(unicode), self.contains(uniChar) {
result.append(Character(uniChar))
}
}
}
return result
}
}
print(CharacterSet.uppercaseLetters.description)
//<Foundation._SwiftNSCharacterSet: 0x6000000271a0>
print(String(CharacterSet.vowels.characters))
//AEIOUYaeiouy
print(CharacterSet.vowels.characters)
// ["A", "E", "I", "O", "U", "Y", "a", "e", "i", "o", "u", "y"]