Remove support for older Swift versions

Parchment/Classes/PagingOptions.swift

@@ -106,30 +106,16 @@ public struct PagingOptions {
     /// view controller. _Default: .horizontal_
     public var contentNavigationOrientation: PagingNavigationOrientation
 
-    #if swift(>=4.2)
-        public var scrollPosition: UICollectionView.ScrollPosition {
-            switch selectedScrollPosition {
-            case .left:
-                return UICollectionView.ScrollPosition.left
-            case .right:
-                return UICollectionView.ScrollPosition.right
-            case .preferCentered, .center:
-                return UICollectionView.ScrollPosition.centeredHorizontally
-            }
+    public var scrollPosition: UICollectionView.ScrollPosition {
+        switch selectedScrollPosition {
+        case .left:
+            return UICollectionView.ScrollPosition.left
+        case .right:
+            return UICollectionView.ScrollPosition.right
+        case .preferCentered, .center:
+            return UICollectionView.ScrollPosition.centeredHorizontally
         }
-
-    #else
-        public var scrollPosition: UICollectionViewScrollPosition {
-            switch selectedScrollPosition {
-            case .left:
-                return UICollectionViewScrollPosition.left
-            case .right:
-                return UICollectionViewScrollPosition.right
-            case .preferCentered, .center:
-                return UICollectionViewScrollPosition.centeredHorizontally
-            }
-        }
-    #endif
+    }
 
     public var menuHeight: CGFloat {
         return menuItemSize.height + menuInsets.top + menuInsets.bottom
@@ -174,13 +160,8 @@ public struct PagingOptions {
             insets: UIEdgeInsets(top: 0, left: 8, bottom: 0, right: 8)
         )
 
-        #if swift(>=4.0)
-            font = UIFont.systemFont(ofSize: 15, weight: UIFont.Weight.medium)
-            selectedFont = UIFont.systemFont(ofSize: 15, weight: UIFont.Weight.medium)
-        #else
-            font = UIFont.systemFont(ofSize: 15, weight: UIFontWeightMedium)
-            selectedFont = UIFont.systemFont(ofSize: 15, weight: UIFontWeightMedium)
-        #endif
+        font = UIFont.systemFont(ofSize: 15, weight: UIFont.Weight.medium)
+        selectedFont = UIFont.systemFont(ofSize: 15, weight: UIFont.Weight.medium)
 
         textColor = UIColor.black
         selectedTextColor = UIColor(red: 3 / 255, green: 125 / 255, blue: 233 / 255, alpha: 1)

Parchment/Classes/PagingSizeCache.swift

@@ -12,13 +12,8 @@ class PagingSizeCache {
     init(options: PagingOptions) {
         self.options = options
 
-        #if swift(>=4.2)
-            let didEnterBackground = UIApplication.didEnterBackgroundNotification
-            let didReceiveMemoryWarning = UIApplication.didReceiveMemoryWarningNotification
-        #else
-            let didEnterBackground = NSNotification.Name.UIApplicationDidEnterBackground
-            let didReceiveMemoryWarning = NSNotification.Name.UIApplicationDidReceiveMemoryWarning
-        #endif
+        let didEnterBackground = UIApplication.didEnterBackgroundNotification
+        let didReceiveMemoryWarning = UIApplication.didReceiveMemoryWarningNotification
 
         NotificationCenter.default.addObserver(self,
                                                selector: #selector(applicationDidEnterBackground(notification:)),

Parchment/Classes/PagingView.swift

@@ -67,11 +67,7 @@ open class PagingView: UIView {
             "pageView": pageView,
         ]
 
-        #if swift(>=4.2)
-            let formatOptions = NSLayoutConstraint.FormatOptions()
-        #else
-            let formatOptions = NSLayoutFormatOptions()
-        #endif
+        let formatOptions = NSLayoutConstraint.FormatOptions()
 
         let horizontalCollectionViewContraints = NSLayoutConstraint.constraints(
             withVisualFormat: "H:|[collectionView]|",

Parchment/Classes/PagingViewController.swift

@@ -477,15 +477,9 @@ open class PagingViewController:
     open override func viewDidLoad() {
         super.viewDidLoad()
 
-        #if swift(>=4.2)
-            addChild(pageViewController)
-            pagingView.configure()
-            pageViewController.didMove(toParent: self)
-        #else
-            addChildViewController(pageViewController)
-            pagingView.configure()
-            pageViewController.didMove(toParentViewController: self)
-        #endif
+        addChild(pageViewController)
+        pagingView.configure()
+        pageViewController.didMove(toParent: self)
 
         pageViewController.delegate = self
         pageViewController.dataSource = self

Parchment/Structs/PagingDiff.swift

@@ -68,20 +68,11 @@ struct PagingDiff {
     }
 
     private func diff(visibleItems: PagingItems, cache: [Int: PagingItem]) -> [IndexPath] {
-        #if swift(>=4.1)
-            return visibleItems.items.compactMap { item in
-                if cache[item.identifier] == nil {
-                    return visibleItems.indexPath(for: item)
-                }
-                return nil
-            }
-        #else
-            return visibleItems.items.flatMap { item in
-                if cache[item.hashValue] == nil {
-                    return visibleItems.indexPath(for: item)
-                }
-                return nil
+        return visibleItems.items.compactMap { item in
+            if cache[item.identifier] == nil {
+                return visibleItems.indexPath(for: item)
             }
-        #endif
+            return nil
+        }
     }
 }