Convert UTF-8 encoded NSData to NSString

Question

I have UTF-8 encoded NSData from windows server and I want to convert it to NSString for iPhone  Since data contains characters  like a degree symbol  which have different values on both platforms  how do I convert data to string

User · Answer

The Swift version from String to Data and back to String:

Xcode 10.1 • Swift 4.2.1

extension Data {
    var string: String? {
        return String(data: self, encoding: .utf8)
    }
}

extension StringProtocol {
    var data: Data {
        return Data(utf8)
    }
}

extension String {
    var base64Decoded: Data? {
        return Data(base64Encoded: self)
    }
}

Playground

let string = "Hello World"                                  // "Hello World"
let stringData = string.data                                // 11 bytes
let base64EncodedString = stringData.base64EncodedString()  // "SGVsbG8gV29ybGQ="
let stringFromData = stringData.string                      // "Hello World"

let base64String = "SGVsbG8gV29ybGQ="
if let data = base64String.base64Decoded {
    print(data)                                    //  11 bytes
    print(data.base64EncodedString())              // "SGVsbG8gV29ybGQ="
    print(data.string ?? "nil")                    // "Hello World"
}

let stringWithAccent = "Olá Mundo"                          // "Olá Mundo"
print(stringWithAccent.count)                               // "9"
let stringWithAccentData = stringWithAccent.data            // "10 bytes" note: an extra byte for the acute accent
let stringWithAccentFromData = stringWithAccentData.string  // "Olá Mundo\n"

User · Answer

If the data is not null-terminated  you should use -initWithData encoding  NSString  newStr     NSString alloc  initWithData theData encoding NSUTF8StringEncoding    If the data is null-terminated  you should instead use -stringWithUTF8String  to avoid the extra  0 at the end  NSString  newStr    NSString stringWithUTF8String  theData bytes      Note that if the input is not properly UTF-8-encoded  you will get nil    Swift variant  let newStr   String data  data  encoding   utf8     note that  newStr  is a  String    not a  String    If the data is null-terminated  you could go though the safe way which is remove the that null character  or the unsafe way similar to the Objective-C version above     safe way  provided data is  0-terminated let newStr1   String data  data subdata in  0    lt  data count - 1   encoding   utf8     unsafe way  provided data is  0-terminated let newStr2   data withUnsafeBytes String init utf8String

User · Answer

Sometimes  the methods in the other answers don t work  In my case  I m generating a signature with my RSA private key and the result is NSData  I found that this seems to work   Objective-C  NSData  signature  NSString  signatureString    signature base64EncodedStringWithOptions 0     Swift  let signatureString   signature base64EncodedStringWithOptions nil

User · Answer

With Swift 5  you can use String s init data encoding   initializer in order to convert a Data instance into a String instance using UTF-8  init data encoding   has the following declaration   init  data  Data  encoding  String Encoding       Returns a String initialized by converting given data into Unicode characters using a given encoding    The following Playground code shows how to use it   import Foundation  let json          firstName     John    lastName     Doe         let data   json data using  String Encoding utf8    let optionalString   String data  data  encoding  String Encoding utf8  print String describing  optionalString        prints   Optional    n  firstName       John    n  lastName       Doe   n

User · Answer

Just to summarize  here s a complete answer  that worked for me   My problem was that when I used    NSString stringWithUTF8String  char   data bytes     The string I got was unpredictable   Around 70  it did contain the expected value  but too often it resulted with Null or even worse  garbaged at the end of the string   After some digging I switched to     NSString alloc  initWithBytes  char   data bytes length data length encoding NSUTF8StringEncoding     And got the expected result every time

User · Answer

You could call this method     id stringWithUTF8String  const char   bytes

User · Answer

I humbly submit a category to make this less annoying    interface NSData  EasyUTF8      Safely decode the bytes into a UTF8 string -  NSString   asUTF8String    end   and   implementation NSData  EasyUTF8   -  NSString   asUTF8String       return   NSString alloc  initWithData self encoding NSUTF8StringEncoding           end    Note that if you re not using ARC you ll need an autorelease there    Now instead of the appallingly verbose   NSData  data         NSString alloc  initWithData data encoding NSUTF8StringEncoding     You can do   NSData  data        data asUTF8String

[ios] Convert UTF-8 encoded NSData to NSString

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