Table of contents

Swift 4.2 Updates

#9 Array Functions
#8 Build configuration import testing
#7 Target environment testing
#6 Derived collections of enum cases
#5 Warning and error diagnostic directives
#4 Random number generation and shuffling
#3 Boolean toggling
#2 In-place collection element removal
#1 Checking sequence elements match a condition

#9 Array Functions

1. Map

Use map to loop over a collection and apply the same operation to each element in the collection.

let arrayOfInt = [2,3,4,5,4,7,2]
let newArrUsingMap = arrayOfInt.map { $0 * 10 } // where $0 is enumrated object of an array/Sequence
// prints [20, 30, 40, 50, 40, 70, 20]

2. Filter

Use filter to loop over a collection and return an Array containing only those elements that match an include condition.

let arr = ["Hello","Bye","Halo"]
let filtered = arr.filter { $0.contains("lo") }
// prints ["Hello", "Halo"] 

3. Flatmap

Flatmap is used to flatten a collection of collections . But before flattening the collection, we can apply map to each elements. Read it like : map + (Flat the collection)

[“abc”,”def”,”ghi”].flatMap { $0.uppercased() }
// output : ["A", "B", "C", "D", "E", "F", "G", "H", "I"] but only map function output would be output: [“ABC”, “DEF”, “GHI”]

All function in one line ;)

let arrayOfArray = [[2,1],[4]]
let sum = arrayOfArray.flatMap{$0}.filter{$0 % 2 == 0}.map{$0 * $0}
print(sum.reduce(0, +)) //20

#8 Build configuration import testing

#if canImport(SpriteKit)
   // this will be true for iOS, macOS, tvOS, and watchOS
#else
   // this will be true for other platforms, such as Linux
#endif

#7 Target environment testing

#if targetEnvironment(simulator)
   // code for the simulator here
#else
   // code for real devices here
#endif

#6 Derived collections of enum cases

enum Developers: CaseIterable {
    case vishal, avadhesh, sandeep, anil
}

for developer in Developers.allCases {
    print("iOS Developer - \(developer).")
}

#5 Warning and error diagnostic directives

func encrypt(_ string: String, with password: String) -> String {
    #warning("This is terrible method of encryption")
    return password + String(string.reversed()) + password
}

struct Configuration {
    var apiKey: String {
        #error("Please enter your API key below then delete this line.")
        return "Enter your key here"
    }
} 

#4 Random number generation and shuffling

let randomInt = Int.random(in: 1..<5)

Similar methods exist for Float, Double, and CGFloat:

let randomFloat = Float.random(in: 1..<10)
let randomDouble = Double.random(in: 1...100)
let randomCGFloat = CGFloat.random(in: 1...1000)

#3 Boolean toggling

var loggedIn = false
loggedIn.toggle()

#2 In-place collection element removal

var developers = ["Avadhesh", "Vishal", "Sandeep", "Anil", "Prashant"]
developers.removeAll { $0.hasPrefix("Sandeep") }
print(developers)
// "["Avadhesh", "Vishal", "Anil", "Prashant"]\n"

#1 Checking sequence elements match a condition

let scores = [80, 88, 95, 92]
let passed = scores.allSatisfy { $0 >= 85 }