lexuanquynh

let numbers = [0, 1, 2, 3]
numbers.filter { number in number == 1 }.isEmpty == false
numbers.first(where: { number in number == 1 }) != nil

lexuanquynh

let numbers = [0, 1, 2, 3]
numbers.contains(1)

lexuanquynh

let firstWhere = collectionOfNumbers.first(where: { $0 % 2 == 0 })
 print(firstWhere) // Prints: 2

lexuanquynh

let collectionOfNumbers = (1…1000000)
 let lazyFirst = collectionOfNumbers.lazy
     .filter {
         print("filter")
         return $0 % 2 == 0
     }.first
 print(lazyFirst) // Prints: 2

lexuanquynh

let modifiedNumbers = numbers
     .filter { number in
         print("Lazy Even number filter")
         return number % 2 == 0
     }.map { number -> Int in
         print("Lazy Doubling the number")
         return number * 2
     }
 print(modifiedNumbers.first!)
 print(modifiedNumbers.first!)

lexuanquynh

let modifiedLazyNumbers = numbers.lazy
     .filter { number in
         print("Lazy Even number filter")
         return number % 2 == 0
     }.map { number -> Int in
         print("Lazy Doubling the number")
         return number * 2
     }
 print(modifiedLazyNumbers.first!)
 print(modifiedLazyNumbers.first!)

lexuanquynh

let places = ["Ho Chi Minh", "Ha Noi", "Hue", "Da Nang", "Vung Tau", "Nha Trang"]
        places
             .filter { place in
                 print("filtered name")
                 return place.lowercased().first == "h"
             }.forEach { place in
                 print("Fetch image for \(place)")
             }
             
             /*

lexuanquynh

 let places = ["Ho Chi Minh", "Ha Noi", "Hue", "Da Nang", "Vung Tau", "Nha Trang"]
        places.lazy
             .filter { place in
                 print("filtered name")
                 return place.lowercased().first == "h"
             }.forEach { place in
                 print("Fetch image for \(place)")
             }
             /*
             Ket qua:

lexuanquynh

print(modifiedLazyNumbers.first!)
 /*
  Prints:
  Lazy Even number filter
  Lazy Even number filter
  Lazy Doubling the number
  4
  */

lexuanquynh

let modifiedLazyNumbers = numbers.lazy
     .filter { number in
         print("Lazy Even number filter")
         return number % 2 == 0
     }.map { number -> Int in
         print("Lazy Doubling the number")
         return number * 2
     }
 print(modifiedLazyNumbers)
 // Prints: