Combining strings
let aString = "Hello"
// Let's play with strings today
// we can combine strings using the + operator
let newString = aString + " swift lovers" // "Hello swift lovers"
// string interpolaton can also be used to combine strings
let a = "BAT"
let b = "MAN"
println("\(a) + \(b) = \(a + b)")
// BAT + MAN = BATMAN
We have an array with animal names. Let’s combine all the names in one string separated by commas.
let animals = ["cat", "dog", "turtle", "swift", "elephant"]
// Solution 1
var result: String = ""
for animal in animals {
if countElements(result) > 0 {
result += ","
}
result += animal
}
// result is "cat,dog,turtle,swift,elephant"
// Solution 2
println("a list of animals: " + ",".join(animals))
// a list of animals: cat,dog,turtle,swift,elephant
// or we can get fancy and print an unordered list
println("\n".join(animals.map({ "• " + $0})))
//• cat
//• dog
//• turtle
//• swift
//• elephant
// We can make the list capitalized
let capitalizedAnimals = animals.map({ $0.capitalizedString })
println("\n".join(capitalizedAnimals.map({ "• " + $0})))
//• Cat
//• Dog
//• Turtle
//• Swift
//• Elephant
// And sorted
let sortedAnimals = capitalizedAnimals.sorted({ (first, second) -> Bool in
return first < second
})
println("\n".join(sortedAnimals.map({ "• " + $0})))
//• Cat
//• Dog
//• Elephant
//• Swift
//• Turtle
In Swift you can’t multiply a String with a scalar, but you can define operators. Let’s make "cat" * 3 work.
func *(string: String, scalar: Int) -> String {
let array = Array(count: scalar, repeatedValue: string)
return "".join(array)
}
println("cat " * 3 + "dog " * 2)
// cat cat cat dog dog
This operator looks helpful if you want to indent your output. Let’s look at how we can show a binary tree.
// A binary tree of order 1 is just one node
// A binary tree of order > 1 has one node in the middle
// and two binary trees one order smaller before and after
func printTree(height: Int, padding: Int) {
if height == 1 {
println(" " * padding + "*")
} else {
printTree(height - 1, padding + 1)
println(" " * padding + "*")
printTree(height - 1, padding + 1)
}
}
printTree(5, 0)
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
//*
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
// *
Working with characters
A quick reminder, you can use lowercaseString and uppercaseString to create a new string in which all the letters are lowercase or uppercase.
let name = "We ❤ Swift"
let lowercase = name.lowercaseString // "we ❤ swift"
let uppercase = name.uppercaseString // "WE ❤ SWIFT"
Let’s take a simple challenge. Given a string create a new one with all the characters in reverse order.
var inReverse = ""
for letter in "We ❤ Swift" {
println(letter)
inReverse = "\(letter)" + inReverse
}
println(inReverse)
// "tfiwS ❤ eW"
Given a string make all the vowels uppercase.
var bigVoewls = ""
for c in "Let's make all the vowels in this string upper case!" {
var toAdd = "\(c)"
switch toAdd.lowercaseString {
case "a", "e", "i", "o", "u":
toAdd = toAdd.uppercaseString
default:
break
}
bigVoewls += toAdd
}
println(bigVoewls)
// LEt's mAkE All thE vOwEls In thIs strIng UppEr cAsE!
Given a list of names (like your contect list) and a string, find all the names that start with that string.
let contacts = ["Alec", "Annalee", "Anya", "Arlie", "Blaine", "Burton", "Cecily", "Deana",
"Deirdre", "Elena", "Elodia", "Francina", "Freeman", "Herbert", "Iona", "Jacqui", "Janna",
"Jeneva", "Karla", "Katelin", "Kathaleen", "Kesha", "Kum", "Lilliam", "Mardell", "Margarite",
"Margy", "Marta", "Maryalice", "Mellisa", "Melodee", "Miguel", "Millie", "Myong", "Nakita",
"Nancy", "Nicolasa", "Noemi", "Roselia", "Sade", "Shalonda", "Shawn", "Siobhan", "Tanna",
"Thu", "Vanesa", "Vonnie", "Wade", "Winford", "Xiomara"]
let prefix = "ma"
// Case sensitive
contacts.filter({ contact in
contact.hasPrefix(prefix)
})
// has 0 matches
// Case unsensitive
let lowercasePrefix = prefix.lowercaseString
contacts.filter({ contact in
contact.lowercaseString.hasPrefix(lowercasePrefix)
})
// has 5 matches -> "Mardell", "Margarite", "Margy", "Marta", "Maryalice"
If you want to read more about filter and other high order functions you can read this article.
Find the state that has the state that has the most vowels in its name. To make things simple we are going to assume that y is not a voewl
let states = ["Alabama", "Alaska", "Arizona", "Arkansas", "California", "Colorado", "Connecticut", "Delaware", "Florida", "Georgia", "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas", "Kentucky", "Louisiana", "MaineME", "Maryland", "Massachuset", "Michigan", "Minnesota", "Mississippi", "Missouri", "Montana", "Nebraska", "NevadaNV", "New Hampshi", "New Jersey", "New Mexico", "New York", "North Carolina", "North Dakota", "Ohio", "Oklahoma", "Oregon", "Pennsylvania", "Rhode Island", "South Carolina", "South Dakota", "Tennessee", "Texas", "Utah", "Vermont", "Virginia", "Washington", "West Virginia", "Wisconsin", "Wyoming", "District of Columbia"]
func numberOfVowels(string: String) -> Int {
var nVowels = 0
for ch in string {
switch "\(ch)".lowercaseString {
case "a", "e", "i", "o", "u":
nVowels++
default:
break
}
}
return nVowels
}
let theStateWithMostVowles = states.reduce(("", 0), combine: { (res, state) in
let (best, count) = res
let nVowels = numberOfVowels(state)
if nVowels > count {
return (state, nVowels)
} else {
return (best, count)
}
})
District of Columbia is the state with the most vowels. How about the state with the most consecutive consonants.
func maxConsecutiveConsonants(string: String) -> Int {
var best = 0
var current = 0
for ch in string {
switch "\(ch)".lowercaseString {
case "a", "e", "i", "o", "u":
if current > best {
best = current
}
current = 0
default:
current++
break
}
}
if current > best {
best = current
}
return best
}
let theStateWithMostConsecutiveConsonants = states.reduce(("", 0), combine: { (res, state) in
let (best, count) = res
let nVowels = maxConsecutiveConsonants(state)
if nVowels > count {
return (state, nVowels)
} else {
return (best, count)
}
})
Nice article.
let sortedAnimals = capitalizedAnimals.sorted({ (first, second) -> Bool in
return first < second
can also be simplified as
let sortedAnimals = capitalizedAnimals.sorted(<)
Nice! I haven’t seen that one before. I only got it as short as
let sortedAnimals = animals.sorted { $0 < $1 }
let aString = “Hello”
// Let’s play with strings today
// we can combine strings using the + operator
let newString = str + ” swift lovers” // “Hello swift lovers”
where is “str”? It should be “aString”
Thank you!