diff --git a/README.md b/README.md
index 85a0441..fe73453 100644
--- a/README.md
+++ b/README.md
@@ -165,7 +165,7 @@ let data = binFile.readData()!
 
 ## Error handling
 
-`touch`/`remove`/`copyTo`/`writeTo`/`mkdir` returns `Result` Object.
+`touch`/`remove`/`copyTo`/`writeTo`/`mkdir` returns `Result` as Enum.
 
 If operation is success, `Result` has `value` property.
 If operation is failure,`Result` has `error` property.
@@ -188,7 +188,7 @@ Path.documentsDir["subdir"].mkdir()
     .onSuccess({ (value:Path) in 
         println( value )
     })
-    .onFailure({ (error:String) in 
+    .onFailure({ (error:NSError) in 
         println( error )
     })
 ````
diff --git a/SwiftFilePath/Path.swift b/SwiftFilePath/Path.swift
index de481fb..7784c1c 100644
--- a/SwiftFilePath/Path.swift
+++ b/SwiftFilePath/Path.swift
@@ -59,16 +59,16 @@ public class Path {
         return path_string
     }
     
-    public func remove() -> Result<Path,String> {
+    public func remove() -> Result<Path,NSError> {
         assert(self.exists,"To remove file, file MUST be exists")
         var error: NSError?
         let result = fileManager.removeItemAtPath(path_string, error:&error)
         return result
             ? Result(success: self)
-            : Result(failure: "Failed to remove file.<error:\(error?.localizedDescription) path:\(path_string)>");
+            : Result(failure: error!);
     }
     
-    public func copyTo(toPath:Path) -> Result<Path,String> {
+    public func copyTo(toPath:Path) -> Result<Path,NSError> {
         assert(self.exists,"To copy file, file MUST be exists")
         var error: NSError?
         let result = fileManager.copyItemAtPath(path_string,
@@ -76,10 +76,10 @@ public class Path {
              error: &error)
         return result
             ? Result(success: self)
-            : Result(failure: "Failed to copy file.<error:\(error?.localizedDescription) from-path:\(path_string) to-path:\(toPath)>");
+            : Result(failure: error!)
     }
     
-    public func moveTo(toPath:Path) -> Result<Path,String> {
+    public func moveTo(toPath:Path) -> Result<Path,NSError> {
         assert(self.exists,"To move file, file MUST be exists")
         var error: NSError?
         let result = fileManager.moveItemAtPath(path_string,
@@ -87,7 +87,7 @@ public class Path {
              error: &error)
         return result
             ? Result(success: self)
-            : Result(failure: "Failed to move file.<error:\(error?.localizedDescription) from-path:\(path_string) to-path:\(toPath)>");
+            : Result(failure: error!)
     }
     
     private func loadAttributes() -> NSDictionary? {
diff --git a/SwiftFilePath/PathExtensionDir.swift b/SwiftFilePath/PathExtensionDir.swift
index 575a036..9ce89f4 100644
--- a/SwiftFilePath/PathExtensionDir.swift
+++ b/SwiftFilePath/PathExtensionDir.swift
@@ -71,10 +71,7 @@ extension Path: SequenceType {
         return self.content(path)
     }
     
-    public func mkdir() -> Result<Path,String> {
-        if( self.exists ){
-            return Result(failure: "Already exists.<path:\(path_string)>")
-        }
+    public func mkdir() -> Result<Path,NSError> {
         var error: NSError?
         let result = fileManager.createDirectoryAtPath(path_string,
             withIntermediateDirectories:true,
@@ -83,7 +80,7 @@ extension Path: SequenceType {
         )
         return result
             ? Result(success: self)
-            : Result(failure: "Failed to mkdir.< error:\(error?.localizedDescription) path:\(path_string) >");
+            : Result(failure: error!)
         
     }
     
diff --git a/SwiftFilePath/PathExtensionFile.swift b/SwiftFilePath/PathExtensionFile.swift
index bf71a05..d3d29bc 100644
--- a/SwiftFilePath/PathExtensionFile.swift
+++ b/SwiftFilePath/PathExtensionFile.swift
@@ -13,14 +13,14 @@ extension  Path {
         return path_string.pathExtension
     }
     
-    public func touch() -> Result<Path,String> {
+    public func touch() -> Result<Path,NSError> {
         assert(!self.isDir,"Can NOT touch to dir")
         return self.exists
             ? self.updateModificationDate()
             : self.createEmptyFile()
     }
     
-    public func updateModificationDate(date: NSDate = NSDate() ) -> Result<Path,String>{
+    public func updateModificationDate(date: NSDate = NSDate() ) -> Result<Path,NSError>{
         var error: NSError?
         let result = fileManager.setAttributes(
             [NSFileModificationDate :date],
@@ -29,17 +29,11 @@ extension  Path {
         )
         return result
             ? Result(success: self)
-            : Result(failure: "Failed to modify file.< error:\(error?.localizedDescription) path:\(path_string) >");
+            : Result(failure: error!)
     }
     
-    private func createEmptyFile() -> Result<Path,String>{
-        let result = fileManager.createFileAtPath(path_string,
-            contents:NSData(),
-            attributes:nil
-        )
-        return result
-            ? Result(success: self)
-            : Result(failure: "Failed to create file:\(path_string)");
+    private func createEmptyFile() -> Result<Path,NSError>{
+        return self.writeString("")
     }
     
     // MARK: - read/write String
@@ -58,7 +52,7 @@ extension  Path {
         return read
     }
     
-    public func writeString(string:String) -> Result<Path,String> {
+    public func writeString(string:String) -> Result<Path,NSError> {
         assert(!self.isDir,"Can NOT write data from  dir")
         var error: NSError?
         let result = string.writeToFile(path_string,
@@ -67,7 +61,7 @@ extension  Path {
             error: &error)
         return result
             ? Result(success: self)
-            : Result(failure: "Failed to write file.< error:\(error?.localizedDescription) path:\(path_string) >");
+            : Result(failure: error!)
     }
     
     // MARK: - read/write NSData
@@ -77,12 +71,13 @@ extension  Path {
         return NSData(contentsOfFile: path_string)
     }
     
-    public func writeData(data:NSData) -> Result<Path,String> {
+    public func writeData(data:NSData) -> Result<Path,NSError> {
         assert(!self.isDir,"Can NOT write data from  dir")
-        let result = data.writeToFile(path_string, atomically:true)
+        var error: NSError?
+        let result = data.writeToFile(path_string, options:.DataWritingAtomic, error: &error)
         return result
             ? Result(success: self)
-            : Result(failure: "Failed to write file.< path:\(path_string) >");
+            : Result(failure: error!)
     }
     
 }
diff --git a/SwiftFilePathTests/SwiftFilePathTests.swift b/SwiftFilePathTests/SwiftFilePathTests.swift
index a4cbb3c..e760f5b 100644
--- a/SwiftFilePathTests/SwiftFilePathTests.swift
+++ b/SwiftFilePathTests/SwiftFilePathTests.swift
@@ -122,6 +122,7 @@ class SwiftFilePathTests: XCTestCase {
             XCTAssertFalse( file.exists )
         }
         
+        
     }
     
     func testMkdirAndRemove(){
@@ -407,6 +408,7 @@ class SwiftFilePathTests: XCTestCase {
                 XCTAssertEqual(error,"NG!")
             })
         
+        
         XCTAssertTrue( result.isFailure )
         XCTAssertEqual( result.error!, "NG!" )
         XCTAssertTrue( callOnFailure )