diff --git a/FDFullscreenPopGesture/UINavigationController+FDFullscreenPopGesture.m b/FDFullscreenPopGesture/UINavigationController+FDFullscreenPopGesture.m
index 914f217..36f6514 100644
--- a/FDFullscreenPopGesture/UINavigationController+FDFullscreenPopGesture.m
+++ b/FDFullscreenPopGesture/UINavigationController+FDFullscreenPopGesture.m
@@ -23,6 +23,18 @@
 #import "UINavigationController+FDFullscreenPopGesture.h"
 #import <objc/runtime.h>
 
+static void fd_methodSwizzling(Class class, SEL originalSelector, SEL swizzledSelector) {
+    Method originalMethod = class_getInstanceMethod(class, originalSelector);
+    Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
+    
+    BOOL success = class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
+    if (success) {
+        class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
+    } else {
+        method_exchangeImplementations(originalMethod, swizzledMethod);
+    }
+}
+
 @interface _FDFullscreenPopGestureRecognizerDelegate : NSObject <UIGestureRecognizerDelegate>
 
 @property (nonatomic, weak) UINavigationController *navigationController;
@@ -86,15 +98,7 @@ + (void)load
         SEL originalSelector = @selector(viewWillAppear:);
         SEL swizzledSelector = @selector(fd_viewWillAppear:);
         
-        Method originalMethod = class_getInstanceMethod(class, originalSelector);
-        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
-        
-        BOOL success = class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
-        if (success) {
-            class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
-        } else {
-            method_exchangeImplementations(originalMethod, swizzledMethod);
-        }
+        fd_methodSwizzling(class, originalSelector, swizzledSelector);
     });
 }
 
@@ -132,15 +136,7 @@ + (void)load
         SEL originalSelector = @selector(pushViewController:animated:);
         SEL swizzledSelector = @selector(fd_pushViewController:animated:);
         
-        Method originalMethod = class_getInstanceMethod(class, originalSelector);
-        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
-        
-        BOOL success = class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
-        if (success) {
-            class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
-        } else {
-            method_exchangeImplementations(originalMethod, swizzledMethod);
-        }
+        fd_methodSwizzling(class, originalSelector, swizzledSelector);
     });
 }