[Swift] 필수 개념 (feat. Coding Test)

String

 

✅ Array: An ordered, random-access collection.

Preinitialized with a fixed number of default values

var digitCounts = Array(repeating: 0, count: 10)
print(digitCounts)
// Prints "[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]"

Accessing Array Values

for in

let streets = ["Albemarle", "Brandywine", "Chesapeake"]

for street in streets {
    print("I don't live on \(street).")
}
// Prints "I don't live on Albemarle."
// Prints "I don't live on Brandywine."
// Prints "I don't live on Chesapeake."

.isEmpty .count

let oddNumbers = [1, 3, 5, 7, 9, 11, 13, 15]

if oddNumbers.isEmpty {
    print("I don't know any odd numbers.")
} else {
    print("I know \(oddNumbers.count) odd numbers.")
}
// Prints "I know 8 odd numbers."

.first .last

if let firstElement = oddNumbers.first, let lastElement = oddNumbers.last {
    print(firstElement, lastElement, separator: ", ")
}
// Prints "1, 15"

var emptyDoubles: [Double] = []
print(emptyDoubles.first, emptyDoubles.last, separator: ", ")
// Prints "nil, nil"

Adding and Removing Elements

.append() .append(contentsOf: ) .insert(, at: )

.remove(at: ) .removeLast(),

 

.firstIndex(of: )

var students = ["Ben", "Ivy", "Jordell"]

students.append("Maxime")
students.append(contentsOf: ["Shakia", "William"])
// ["Ben", "Ivy", "Jordell", "Maxime", "Shakia", "William"]

students.insert("Liam", at: 3)
// ["Ben", "Ivy", "Jordell", "Liam", "Maxime", "Shakia", "William"]

students.remove(at: 0)
// ["Ivy", "Jordell", "Liam", "Maxime", "Shakia", "William"]

students.removeLast()
// ["Ivy", "Jordell", "Liam", "Maxime", "Shakia"]

if let i = students.firstIndex(of: "Maxime") {
    students[i] = "Max"
}
// ["Ivy", "Jordell", "Liam", "Max", "Shakia"]

✅  Set: An unordered collection of unique elements.

초기화

let ingredients: Set = ["cocoa beans", "sugar", "cocoa butter", "salt"]
if ingredients.contains("sugar") {
    print("No thanks, too sweet.")
}
// Prints "No thanks, too sweet."

 

 

연산자

.contains(_:)

== .isSubset(of: ) .isSuperset(of: ) isStrictSubset(of:) isStrictSuperset(of:) isDisjoint(with:)

.union(_: ) .intersection(_: ) .symmetricDifference(_: ) .subtracting(:_ )

var primes: Set = [2, 3, 5, 7]

// Tests whether primes is a subset of a Range<Int>
print(primes.isSubset(of: 0..<10))
// Prints "true"

// Performs an intersection with an Array<Int>
let favoriteNumbers = [5, 7, 15, 21]
print(primes.intersection(favoriteNumbers))
// Prints "[5, 7]"

 

Sequence and Collection Operations

if primes.isEmpty {
    print("No primes!")
} else {
    print("We have \(primes.count) primes.")
}
// Prints "We have 4 primes."

let primesSum = primes.reduce(0, +)
// 'primesSum' == 17

let primeStrings = primes.sorted().map(String.init)
// 'primeStrings' == ["2", "3", "5", "7"]

for number in primes {
    print(number)
}
// Prints "5"
// Prints "7"
// Prints "2"
// Prints "3"

let primesStrings = primes.map(String.init)
// 'primesStrings' is of type Array<String>
let primesStringsSet = Set(primes.map(String.init))
// 'primesStringsSet' is of type Set<String>

 

✅  Dictionary: A collection whose elements are key-value pairs.

초기화

var responseMessages = [200: "OK",
                        403: "Access forbidden",
                        404: "File not found",
                        500: "Internal server error"]

var emptyDict: [String: String] = [:]

Getting and Setting Dictionary Values

print(responseMessages[200])
// Prints "Optional("OK")"

let httpResponseCodes = [200, 403, 301]
for code in httpResponseCodes {
    if let message = responseMessages[code] {
        print("Response \(code): \(message)")
    } else {
        print("Unknown response \(code)")
    }
}
// Prints "Response 200: OK"
// Prints "Response 403: Access forbidden"
// Prints "Unknown response 301"

추가, 삭제

Optional 값으로 나오는 것 주의

responseMessages[301] = "Moved permanently"
print(responseMessages[301])
// Prints "Optional("Moved permanently")"

삭제: nil 대입

responseMessages[404] = "Not found"
responseMessages[500] = nil
print(responseMessages)
// Prints "[301: "Moved permanently", 200: "OK", 403: "Access forbidden", 404: "Not found"]"

Dictionary.keys

Dictionary[key]?

Dictionary[key]!

var interestingNumbers = ["primes": [2, 3, 5, 7, 11, 13, 17],
                          "triangular": [1, 3, 6, 10, 15, 21, 28],
                          "hexagonal": [1, 6, 15, 28, 45, 66, 91]]
for key in interestingNumbers.keys {
    interestingNumbers[key]?.sort(by: >)
}

print(interestingNumbers["primes"]!)
// Prints "[17, 13, 11, 7, 5, 3, 2]"

key, value 동시 접근

let imagePaths = ["star": "/glyphs/star.png",
                  "portrait": "/images/content/portrait.jpg",
                  "spacer": "/images/shared/spacer.gif"]

for (name, path) in imagePaths {
    print("The path to '\(name)' is '\(path)'.")
}
// Prints "The path to 'star' is '/glyphs/star.png'."
// Prints "The path to 'portrait' is '/images/content/portrait.jpg'."
// Prints "The path to 'spacer' is '/images/shared/spacer.gif'."

.firstIndex(where: Closure)

.hasPrefix(_:)

let glyphIndex = imagePaths.firstIndex(where: { $0.value.hasPrefix("/glyphs") })
if let index = glyphIndex {
    print("The '\(imagePaths[index].key)' image is a glyph.")
} else {
    print("No glyphs found!")
}
// Prints "The 'star' image is a glyph.")

Closure, High Ordered Function

 

 

Reference

• https://developer.apple.com/documentation/swift/string
• https://developer.apple.com/documentation/swift/array
• https://developer.apple.com/documentation/swift/set
• https://developer.apple.com/documentation/swift/dictionary
• https://developer.apple.com/documentation/swift/range