diff --git a/Spring/DesignableTabBarController.swift b/Spring/DesignableTabBarController.swift
index dc55036..0ef83de 100644
--- a/Spring/DesignableTabBarController.swift
+++ b/Spring/DesignableTabBarController.swift
@@ -47,7 +47,7 @@ import UIKit
     @IBInspectable var firstSelectedImage: UIImage? {
         didSet {
             if let image = firstSelectedImage {
-                var tabBarItems = self.tabBar.items as [UITabBarItem]!
+                var tabBarItems = self.tabBar.items as [UITabBarItem]?
                 tabBarItems?[0].selectedImage = image.withRenderingMode(UIImageRenderingMode.alwaysTemplate)
             }
         }
@@ -56,7 +56,7 @@ import UIKit
     @IBInspectable var secondSelectedImage: UIImage? {
         didSet {
             if let image = secondSelectedImage {
-                var tabBarItems = self.tabBar.items as [UITabBarItem]!
+                var tabBarItems = self.tabBar.items as [UITabBarItem]?
                 tabBarItems?[1].selectedImage = image.withRenderingMode(UIImageRenderingMode.alwaysTemplate)
             }
         }
@@ -65,7 +65,7 @@ import UIKit
     @IBInspectable var thirdSelectedImage: UIImage? {
         didSet {
             if let image = thirdSelectedImage {
-                var tabBarItems = self.tabBar.items as [UITabBarItem]!
+                var tabBarItems = self.tabBar.items as [UITabBarItem]?
                 tabBarItems?[2].selectedImage = image.withRenderingMode(UIImageRenderingMode.alwaysTemplate)
             }
         }
@@ -74,7 +74,7 @@ import UIKit
     @IBInspectable var fourthSelectedImage: UIImage? {
         didSet {
             if let image = fourthSelectedImage {
-                var tabBarItems = self.tabBar.items as [UITabBarItem]!
+                var tabBarItems = self.tabBar.items as [UITabBarItem]?
                 tabBarItems?[3].selectedImage = image.withRenderingMode(UIImageRenderingMode.alwaysTemplate)
             }
         }
@@ -83,7 +83,7 @@ import UIKit
     @IBInspectable var fifthSelectedImage: UIImage? {
         didSet {
             if let image = fifthSelectedImage {
-                var tabBarItems = self.tabBar.items as [UITabBarItem]!
+                var tabBarItems = self.tabBar.items as [UITabBarItem]?
                 tabBarItems?[4].selectedImage = image.withRenderingMode(UIImageRenderingMode.alwaysTemplate)
             }
         }
@@ -92,7 +92,9 @@ import UIKit
     override func viewDidLoad() {
         super.viewDidLoad()
         
-        for item in self.tabBar.items as [UITabBarItem]! {
+        guard let items = self.tabBar.items as [UITabBarItem]? else { return }
+        
+        for item in items {
             if let image = item.image {
                 item.image = image.imageWithColor(tintColor: self.normalTint).withRenderingMode(UIImageRenderingMode.alwaysOriginal)
             }
diff --git a/Spring/Misc.swift b/Spring/Misc.swift
index b2a27ce..902e7b3 100644
--- a/Spring/Misc.swift
+++ b/Spring/Misc.swift
@@ -23,7 +23,7 @@
 import UIKit
 
 public extension String {
-    public var length: Int { return self.characters.count }
+    public var length: Int { return self.count }
     
     public func toURL() -> NSURL? {
         return NSURL(string: self)
@@ -73,7 +73,7 @@ public extension UIColor {
         let scanner = Scanner(string: hex)
         var hexValue: CUnsignedLongLong = 0
         if scanner.scanHexInt64(&hexValue) {
-            switch (hex.characters.count) {
+            switch (hex.count) {
             case 3:
                 red   = CGFloat((hexValue & 0xF00) >> 8)       / 15.0
                 green = CGFloat((hexValue & 0x0F0) >> 4)       / 15.0