diff --git a/STNumberLabel.xcodeproj/project.pbxproj b/STNumberLabel.xcodeproj/project.pbxproj
index 4c96497..c6a7335 100644
--- a/STNumberLabel.xcodeproj/project.pbxproj
+++ b/STNumberLabel.xcodeproj/project.pbxproj
@@ -13,10 +13,7 @@
 		EB29E0581BED9B1A002D9DEA /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = EB29E0571BED9B1A002D9DEA /* Assets.xcassets */; };
 		EB29E05B1BED9B1A002D9DEA /* LaunchScreen.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = EB29E0591BED9B1A002D9DEA /* LaunchScreen.storyboard */; };
 		EB29E0641BED9B5A002D9DEA /* STScrollNumberView.swift in Sources */ = {isa = PBXBuildFile; fileRef = EB29E0631BED9B5A002D9DEA /* STScrollNumberView.swift */; };
-		EB2DE4A81BF07F11000766F8 /* CharacterExtension.swift in Sources */ = {isa = PBXBuildFile; fileRef = EB2DE4A71BF07F11000766F8 /* CharacterExtension.swift */; };
 		EB6F9E4E1BEE594C0097630D /* STNumberLabel.swift in Sources */ = {isa = PBXBuildFile; fileRef = EB6F9E4D1BEE594C0097630D /* STNumberLabel.swift */; };
-		EBD69A791BF9BA35000AB73C /* UIViewExtension.swift in Sources */ = {isa = PBXBuildFile; fileRef = EBD69A781BF9BA35000AB73C /* UIViewExtension.swift */; };
-		EBDCFEA61BFEF26B0037332B /* STScrollNumberViewExtension.swift in Sources */ = {isa = PBXBuildFile; fileRef = EBDCFEA51BFEF26B0037332B /* STScrollNumberViewExtension.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -28,10 +25,7 @@
 		EB29E05A1BED9B1A002D9DEA /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.storyboard; name = Base; path = Base.lproj/LaunchScreen.storyboard; sourceTree = "<group>"; };
 		EB29E05C1BED9B1A002D9DEA /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		EB29E0631BED9B5A002D9DEA /* STScrollNumberView.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = STScrollNumberView.swift; sourceTree = "<group>"; };
-		EB2DE4A71BF07F11000766F8 /* CharacterExtension.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CharacterExtension.swift; sourceTree = "<group>"; };
 		EB6F9E4D1BEE594C0097630D /* STNumberLabel.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = STNumberLabel.swift; sourceTree = "<group>"; };
-		EBD69A781BF9BA35000AB73C /* UIViewExtension.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = UIViewExtension.swift; sourceTree = "<group>"; };
-		EBDCFEA51BFEF26B0037332B /* STScrollNumberViewExtension.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = STScrollNumberViewExtension.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -87,22 +81,11 @@
 		EB2DE4A61BF07E6D000766F8 /* STNumberLabel */ = {
 			isa = PBXGroup;
 			children = (
-				EB2DE4A91BF07F1F000766F8 /* Extension */,
 				EB29E0621BED9B1F002D9DEA /* Views */,
 			);
 			name = STNumberLabel;
 			sourceTree = "<group>";
 		};
-		EB2DE4A91BF07F1F000766F8 /* Extension */ = {
-			isa = PBXGroup;
-			children = (
-				EB2DE4A71BF07F11000766F8 /* CharacterExtension.swift */,
-				EBD69A781BF9BA35000AB73C /* UIViewExtension.swift */,
-				EBDCFEA51BFEF26B0037332B /* STScrollNumberViewExtension.swift */,
-			);
-			name = Extension;
-			sourceTree = "<group>";
-		};
 /* End PBXGroup section */
 
 /* Begin PBXNativeTarget section */
@@ -174,9 +157,6 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				EBD69A791BF9BA35000AB73C /* UIViewExtension.swift in Sources */,
-				EB2DE4A81BF07F11000766F8 /* CharacterExtension.swift in Sources */,
-				EBDCFEA61BFEF26B0037332B /* STScrollNumberViewExtension.swift in Sources */,
 				EB29E0531BED9B1A002D9DEA /* ViewController.swift in Sources */,
 				EB29E0641BED9B5A002D9DEA /* STScrollNumberView.swift in Sources */,
 				EB6F9E4E1BEE594C0097630D /* STNumberLabel.swift in Sources */,
diff --git a/STNumberLabel/CharacterExtension.swift b/STNumberLabel/CharacterExtension.swift
deleted file mode 100644
index 6bf56a6..0000000
--- a/STNumberLabel/CharacterExtension.swift
+++ /dev/null
@@ -1,37 +0,0 @@
-//
-//  CharacterExtension.swift
-//  STNumberLabel
-//
-//  Created by DangGu on 15/11/9.
-//  Copyright © 2015年 Donggu. All rights reserved.
-//
-
-import UIKit
-
-extension Character {
-    func intValue() -> Int? {
-        return Int(String(self))
-    }
-    
-    func utf8Value() -> UInt8 {
-        for s in String(self).utf8 {
-            return s
-        }
-        return 0
-    }
-    
-    func utf16Value() -> UInt16 {
-        for s in String(self).utf16 {
-            return s
-        }
-        return 0
-    }
-    
-    func unicodeValue() -> UInt32 {
-        for s in String(self).unicodeScalars {
-            return s.value
-        }
-        return 0
-    }
-}
-
diff --git a/STNumberLabel/STNumberLabel.swift b/STNumberLabel/STNumberLabel.swift
index 7e1c22a..1c4be9f 100644
--- a/STNumberLabel/STNumberLabel.swift
+++ b/STNumberLabel/STNumberLabel.swift
@@ -9,30 +9,39 @@
 import UIKit
 
 class STNumberLabel: UIView {
-    
-    private var digit: Int!
-    var scrollNumberViews: [STScrollNumberView]!
-    
-    internal var font: UIFont!
-    internal var singleNumberSize: CGSize!
-    internal var containerView: UIView!
-    
+
+    private var digit: Int
+    private var scrollNumberViews = [STScrollNumberView]()
+
+    private let font: UIFont
+    private let singleNumberSize: CGSize
+    private var containerView: UIView!
+
     init(frame: CGRect, digit: Int, font: UIFont, singleNumberSize: CGSize) {
         self.digit = digit
         self.font = font
         self.singleNumberSize = singleNumberSize
+
         super.init(frame: frame)
-        setupScrollNumberView()
 
+        self.containerView = setupScrollNumberView()
     }
-    
+
+    required init?(coder aDecoder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}
+
+extension STNumberLabel {
+
     func scrollToNumber(number: Int) {
+
         let numberString = String(number)
         let newDigit = numberString.characters.count
         
         var numberArray: [Int] = []
-        numberString.characters.forEach { (character) -> () in
-            guard let intNumber = character.intValue() else { return }
+        numberString.characters.forEach { character in
+            guard let intNumber = Int(String(character)) else { return }
             numberArray.append(intNumber)
         }
         
@@ -42,41 +51,45 @@ class STNumberLabel: UIView {
                 scrollNumberView.scrollToNumber(numberArray[i])
             }
         }  else {
+
             let diff = newDigit - digit
-            let translate = CGFloat(diff) * (singleNumberSize!.width / 2)
-            
-            UIView.animateWithDuration(0.33, animations: { [unowned self]() -> Void in
-                self.containerView!.center = CGPoint(x: self.containerView!.center.x + translate, y: self.containerView!.center.y)
-                }, completion: { (finished) -> Void in
-                    if finished {
-                        self.constructNewContainerView(newDigit: newDigit, diff: diff, numberArray: numberArray)
-                    }
+            let translate = CGFloat(diff) * (singleNumberSize.width / 2)
+
+            UIView.animateWithDuration(0.33, animations: { [unowned self] in
+                self.containerView.center = CGPoint(x: self.containerView.center.x + translate, y: self.containerView.center.y)
+
+            }, completion: { _ in
+                self.constructNewContainerView(newDigit: newDigit, diff: diff, numberArray: numberArray)
             })
         }
-        
+
     }
     
     // MARK: - helper
-    private func setupScrollNumberView() {
+    private func setupScrollNumberView() -> UIView {
+
         let containerViewFrame = CGRect(origin: CGPointZero, size: CGSize(width: CGFloat(digit) * singleNumberSize.width, height: singleNumberSize.height))
-        containerView = UIView(frame: containerViewFrame)
-        containerView.center = absoluteCenter
-        
-        scrollNumberViews = []
+        let containerView = UIView(frame: containerViewFrame)
+        containerView.center = CGPoint(x: frame.width / 2, y: frame.height / 2)
+
         for i in 0..<digit {
             let numberFrame = CGRect(x: CGFloat(i)*singleNumberSize.width, y: 0, width: singleNumberSize.width, height: singleNumberSize.height)
             let scrollNumberView = STScrollNumberView(frame: numberFrame, font: font)
             scrollNumberViews.append(scrollNumberView)
             containerView.addSubview(scrollNumberView)
         }
-        
+
         addSubview(containerView)
+
+        return containerView
     }
     
     private func constructNewContainerView(newDigit newDigit: Int, diff: Int, numberArray: [Int]) {
+
         let newContainerViewFrame = CGRect(origin: CGPointZero, size: CGSize(width: CGFloat(newDigit) * singleNumberSize.width, height: singleNumberSize.height))
+
         let newContainerView = UIView(frame: newContainerViewFrame)
-        newContainerView.center = absoluteCenter
+        newContainerView.center = CGPoint(x: frame.width / 2, y: frame.height / 2)
         newContainerView.alpha = 0.0
         
         var newSrollNumberView: [STScrollNumberView] = []
@@ -105,27 +118,26 @@ class STNumberLabel: UIView {
                 newContainerView.addSubview(scrollNumberView)
             }
         }
-
         
         addSubview(newContainerView)
-        
-        UIView.animateWithDuration(0.5, delay: 0.0, options: .CurveLinear, animations: { [unowned self]() -> Void in
+
+        UIView.animateWithDuration(0.5, delay: 0.0, options: .CurveLinear, animations: { [unowned self] in
+
             newContainerView.alpha = 1.0
             self.containerView.alpha = 0.0
-            }) { [unowned self](finished) -> Void in
-                self.containerView.removeFromSuperview()
-                self.containerView = newContainerView
-                self.scrollNumberViews = newSrollNumberView
-                self.digit = newDigit
-                
-                for i in 0..<self.scrollNumberViews.count {
-                    let scrollNumberView: STScrollNumberView = self.scrollNumberViews[i]
-                    scrollNumberView.scrollToNumber(numberArray[i])
-                }
-        }
-    }
-    
-    required init?(coder aDecoder: NSCoder) {
-        fatalError("init(coder:) has not been implemented")
+
+        }, completion: { _ in
+
+            self.containerView.removeFromSuperview()
+            self.containerView = newContainerView
+            self.scrollNumberViews = newSrollNumberView
+            self.digit = newDigit
+
+            for i in 0..<self.scrollNumberViews.count {
+                let scrollNumberView: STScrollNumberView = self.scrollNumberViews[i]
+                scrollNumberView.scrollToNumber(numberArray[i])
+            }
+
+        })
     }
 }
diff --git a/STNumberLabel/STScrollNumberView.swift b/STNumberLabel/STScrollNumberView.swift
index 33c0f0c..6832c66 100644
--- a/STNumberLabel/STScrollNumberView.swift
+++ b/STNumberLabel/STScrollNumberView.swift
@@ -9,52 +9,65 @@
 import UIKit
 
 class STScrollNumberView: UIView {
-    var scrollView: UIScrollView!
-    var currentNumber = 0
-    var font: UIFont!
-    let numberIndex: [Int] = [9,8,7,6,5,4,3,2,1,0]
+
+    private let scrollView: UIScrollView
+    private var currentNumber = 0
+    private let font: UIFont
+    private let numberIndex: [Int] = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
     
     init(frame: CGRect, font: UIFont, number: Int) {
+
         self.font = font
         self.currentNumber = number
+        self.scrollView = UIScrollView(frame: CGRect(origin: CGPointZero, size: frame.size))
+
         super.init(frame: frame)
-        
-        scrollView = UIScrollView(frame: bounds)
-        scrollView.contentSize = CGSize(width: self.width, height: self.height*10)
+
+        scrollView.contentSize = CGSize(width: frame.width, height: frame.height * 10)
+
         for i in 0..<10 {
-            let numberFrame = CGRectMake(0, height*CGFloat(i), width, height)
+            let numberFrame = CGRectMake(0, frame.height * CGFloat(i), frame.width, frame.height)
             let label = UILabel(frame: numberFrame)
             label.text = "\(numberIndex[i])"
             label.textAlignment = NSTextAlignment.Center
             label.font = font
             scrollView.addSubview(label)
         }
-        scrollView.contentOffset = CGPoint(x: 0, y: height*CGFloat(numberIndex[currentNumber]))
-        
+
+        scrollView.contentOffset = CGPoint(x: 0, y: frame.height * CGFloat(numberIndex[currentNumber]))
+
         addSubview(scrollView)
     }
-    
+
     convenience init(frame: CGRect, font: UIFont) {
         self.init(frame: frame, font: font, number: 0)
     }
-    
+
+    required init?(coder aDecoder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+
     func scrollToNumber(number: NSInteger) {
-        if number<0 || number > 10 {
+        if number < 0 || number > 10 {
             scrollToNumber(0)
             return
         }
+
         if number == currentNumber {
             return
         }
+
         currentNumber = number
-        UIView.animateWithDuration(1.0, delay: 0.0, options: .CurveEaseOut,
-            animations: { [weak self]() -> Void in
-                guard let weakSelf = self else {return}
-                weakSelf.scrollView.setContentOffset(CGPoint(x: 0, y: weakSelf.height*CGFloat(weakSelf.numberIndex[number])), animated: false)
-            }, completion: nil)
+
+        UIView.animateWithDuration(1.0, delay: 0.0, options: .CurveEaseOut, animations: { [unowned self] in
+                self.scrollView.setContentOffset(CGPoint(x: 0, y: self.frame.height * CGFloat(self.numberIndex[number])), animated: false)
+        }, completion: nil)
     }
-    
-    required init?(coder aDecoder: NSCoder) {
-        super.init(coder: aDecoder)
+
+}
+
+extension STScrollNumberView {
+    func deepCopy() -> STScrollNumberView {
+        return STScrollNumberView(frame: frame, font: font, number: currentNumber)
     }
 }
diff --git a/STNumberLabel/STScrollNumberViewExtension.swift b/STNumberLabel/STScrollNumberViewExtension.swift
deleted file mode 100644
index 3d905e5..0000000
--- a/STNumberLabel/STScrollNumberViewExtension.swift
+++ /dev/null
@@ -1,15 +0,0 @@
-//
-//  STScrollNumberViewExtension.swift
-//  STNumberLabel
-//
-//  Created by DangGu on 15/11/20.
-//  Copyright © 2015年 Donggu. All rights reserved.
-//
-
-import Foundation
-
-extension STScrollNumberView {
-    func deepCopy() -> STScrollNumberView {
-        return STScrollNumberView(frame: frame, font: font, number: currentNumber)
-    }
-}
\ No newline at end of file
diff --git a/STNumberLabel/UIViewExtension.swift b/STNumberLabel/UIViewExtension.swift
deleted file mode 100644
index 0ea1e5c..0000000
--- a/STNumberLabel/UIViewExtension.swift
+++ /dev/null
@@ -1,53 +0,0 @@
-//
-//  UIViewExtension.swift
-//  STNumberLabel
-//
-//  Created by DangGu on 15/11/16.
-//  Copyright © 2015年 Donggu. All rights reserved.
-//
-
-import UIKit
-
-extension UIView {
-    var width: CGFloat {
-        get {
-            return CGRectGetWidth(frame)
-        }
-    }
-    
-    var height: CGFloat {
-        get {
-            return CGRectGetHeight(frame)
-        }
-    }
-    
-    var minX: CGFloat {
-        get {
-            return CGRectGetMinX(frame)
-        }
-    }
-    
-    var minY: CGFloat {
-        get {
-            return CGRectGetMinY(frame)
-        }
-    }
-    
-    var maxX: CGFloat {
-        get {
-            return CGRectGetMaxX(frame)
-        }
-    }
-    
-    var maxY: CGFloat {
-        get {
-            return CGRectGetMaxY(frame)
-        }
-    }
-    
-    var absoluteCenter: CGPoint {
-        get {
-            return CGPoint(x: width / 2, y: height / 2)
-        }
-    }
-}
\ No newline at end of file
diff --git a/STNumberLabel/ViewController.swift b/STNumberLabel/ViewController.swift
index baf2bff..67ab242 100644
--- a/STNumberLabel/ViewController.swift
+++ b/STNumberLabel/ViewController.swift
@@ -16,7 +16,7 @@ class ViewController: UIViewController {
     override func viewDidLoad() {
         super.viewDidLoad()
         numberlabel = STNumberLabel(frame: CGRectMake(150, 200, 200, 50), digit: 4, font: UIFont.systemFontOfSize(22.0), singleNumberSize: CGSize(width: 20, height: 50))
-        numberlabel.center = CGPoint(x: view.width / 2, y: 200)
+        numberlabel.center = CGPoint(x: view.frame.width / 2, y: 200)
         view.addSubview(numberlabel);
     }