sequence

Author: koromiko

Sequence.playground/Contents.swift

@@ -0,0 +1,118 @@
+//: Playground - noun: a place where people can play
+
+import UIKit
+
+struct Beer: CustomDebugStringConvertible {
+    var brandName: String
+    var volume: Int
+    
+    var debugDescription: String {
+        return "\(brandName): \(volume) ml"
+    }
+    
+    public var isCan: Bool {
+        return (self.volume < 350)
+    }
+}
+
+
+struct BeerContainer {
+    let elements: [Beer]
+    var i = 0
+    
+    init(elements: [Beer]) {
+        self.elements = elements
+    }
+}
+
+extension BeerContainer: IteratorProtocol {
+    typealias Element = Beer
+    
+    mutating func next() -> Element? {
+        defer {
+            i+=1
+        }
+        return i<elements.count ? elements[i] : nil
+    }
+}
+
+// Origin
+//struct VendorMachine {
+//    let elements: [Beer]
+//}
+
+// Using IndexingIterator
+//extension VendorMachine: Sequence {
+//    typealias Iterator = IndexingIterator<[Beer]>
+//    
+//    func makeIterator() -> Iterator {
+//        return elements.makeIterator()
+//    }
+//    
+//}
+
+// Try AnyIterator
+//extension VendorMachine: Sequence {
+//    typealias Iterator = AnyIterator<Beer>
+//    
+//    func makeIterator() -> Iterator {
+//        var iterator = elements.makeIterator()
+//        return AnyIterator {
+//            iterator.next()
+//        }
+//    }
+//}
+
+// Use our Iterator
+//extension VendorMachine: Sequence {
+//    typealias Iterator = BeerContainer
+//    
+//    func makeIterator() -> Iterator {
+//        return BeerContainer(elements: self.elements)
+//    }
+//}
+
+struct VendorMachine: Sequence {
+    typealias Iterator = AnyIterator<Beer>
+    
+    let elements: [Beer]
+    
+    func makeIterator() -> Iterator {
+        var i = self.elements.startIndex
+        return AnyIterator {
+            defer {
+                i+=1
+            }
+            return i<self.elements.count ? self.elements[i] : nil
+        }
+    }
+}
+
+
+let aOrionBeer = Beer(brandName: "Orion", volume: 300)
+let aSaporoBeer = Beer(brandName: "Saporo", volume: 380)
+let aTaiwanBeer = Beer(brandName: "TaiwanBeer", volume: 330)
+let aAsahiBeer = Beer(brandName: "Asahi", volume: 420)
+
+
+var aBeerContainer = BeerContainer(elements: [ aOrionBeer, aSaporoBeer, aTaiwanBeer, aAsahiBeer ])
+
+while let aBeer = aBeerContainer.next() {
+    print(aBeer)
+}
+
+
+let aMachine = VendorMachine(elements: [ aOrionBeer, aSaporoBeer, aTaiwanBeer, aAsahiBeer ])
+for beer in aMachine {
+    print(beer)
+}
+
+let sortedBeers = aMachine.sorted { $0.volume>$1.volume }
+print(sortedBeers)
+
+let largeBeers = aMachine.filter { $0.volume>400 }
+print( largeBeers )
+
+let totalVolume = aMachine.reduce(0) { return $0+$1.volume }
+print(totalVolume)
+

Sequence.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>