Introduce color provider to encapsulate check for iOS 13 availability

passKit/Helpers/Colors.swift

@@ -0,0 +1,51 @@
+//
+//  Colors.swift
+//  passKit
+//
+//  Created by Danny Moesch on 01.10.19.
+//  Copyright © 2019 Bob Sun. All rights reserved.
+//
+
+public struct Colors {
+    public static let label: UIColor = {
+        if #available(iOS 13.0, *) {
+            return .label
+        }
+        return .black
+    }()
+
+    public static let secondaryLabel: UIColor = {
+        if #available(iOS 13.0, *) {
+            return .secondaryLabel
+        }
+        return .init(red: 60.0, green: 60.0, blue: 67.0, alpha: 0.6)
+    }()
+
+    public static let systemBackground: UIColor = {
+        if #available(iOS 13.0, *) {
+            return .systemBackground
+        }
+        return .white
+    }()
+
+    public static let secondarySystemBackground: UIColor = {
+        if #available(iOS 13.0, *) {
+            return .secondarySystemBackground
+        }
+        return .init(red: 242.0, green: 242.0, blue: 247.0, alpha: 1.0)
+    }()
+
+    public static let systemRed: UIColor = {
+        if #available(iOS 13.0, *) {
+            return .systemRed
+        }
+        return .red
+    }()
+
+    public static let systemBlue: UIColor = {
+        if #available(iOS 13.0, *) {
+            return .systemBlue
+        }
+        return .blue
+    }()
+}