Base64 Decoding in iOS 7+

Question

I have Encoded text(NSString) using NSData Class new API which is Added in iOS7.

using this

- (NSData *)dataUsingEncoding:(NSStringEncoding)encoding;  

here is my code

NSString *base64EncodedString = [[myText dataUsingEncoding:NSUTF8StringEncoding] base64EncodedStringWithOptions:0];

NSLog(@"%@", base64EncodedString);

I am looking to decode it

Camelopardalis

m_EncodeText: please stop – Aircraft

where have you found base64EncodedStringWithOptions:? – Siracusa

@Siracusa it's there in apple docs developer.apple.com/library/ios/documentation/cocoa/reference/… – Camelopardalis

It seems It happens when I use mac os console application target. Or the old version of sdk/mac os target – Siracusa

Answer 1

Swift 3+

let plainString = "foo"

Encoding

let plainData = plainString.data(using: .utf8)
let base64String = plainData?.base64EncodedString()
print(base64String!) // Zm9v

Decoding

if let decodedData = Data(base64Encoded: base64String!),
   let decodedString = String(data: decodedData, encoding: .utf8) {
  print(decodedString) // foo
}

---

Swift < 3

let plainString = "foo"

Encoding

let plainData = plainString.dataUsingEncoding(NSUTF8StringEncoding)
let base64String = plainData?.base64EncodedStringWithOptions(NSDataBase64EncodingOptions(rawValue: 0))
print(base64String!) // Zm9v

Decoding

let decodedData = NSData(base64EncodedString: base64String!, options: NSDataBase64DecodingOptions(rawValue: 0))
let decodedString = NSString(data: decodedData, encoding: NSUTF8StringEncoding)
print(decodedString) // foo

---

Objective-C

NSString *plainString = @"foo";

Encoding

NSData *plainData = [plainString dataUsingEncoding:NSUTF8StringEncoding];
NSString *base64String = [plainData base64EncodedStringWithOptions:0];
NSLog(@"%@", base64String); // Zm9v

Decoding

NSData *decodedData = [[NSData alloc] initWithBase64EncodedString:base64String options:0];
NSString *decodedString = [[NSString alloc] initWithData:decodedData encoding:NSUTF8StringEncoding];
NSLog(@"%@", decodedString); // foo 

---

Kanal

I don't think this code is clean. I get the warning : "incompatible pointer types initializing NNSTring with an expression of NSData" – Rink

@Rink you must have typed base64EncodedDataWithOptions: instead of base64EncodedStringWithOptions: – Commotion

Thanks for this. Something I just found: a constant kNilOptions is equal to 0 which is arguably more readable than using 0 for options. – Organogenesis

@AdamWaite kNilOptions is defined in MacTypes.h which is a legacy OSX header, so I don't like using it, since I think that header should be removed from the iOS SDK altogether. Anyway, you have a point in saying that is very readable, so feel free to use it. – Kanal

it seems the method base64EncodedStringWithOptions is not url safe base64 – Gesticulate

base64 decoding works only if the string length is a multiple of 4. otherwise NSData returns nil. – Marquee

this code works well But in my case i get xml response from server which are already in base64 encoded .I have decode that data but when i use this method it returns null. can anybody suggest me tackle this problem ??? – Gudgeon

Decoding may not work if there's a new line following the encoded data. See, for example, Decode base64 data encoded in bash. – Approbation

if anyone getting a nil try NSDataBase64DecodingOptions.IgnoreUnknownCharacters i had this issue – Foetid

I was decoding a JWT token, and learned there were a few more fancy steps to decode it. I used the method base64decode from github.com/Wstunes/SwiftyJWT after parsing the JWT token at the periods. – Cl

While decoding the base64String I was getting nil for using NSData *decodedData = [[NSData alloc] initWithBase64EncodedString:base64String options:0]; So, I used NSData *decodedData = [[NSData alloc] initWithBase64EncodedString:base64String options:NSDataBase64DecodingIgnoreUnknownCharacters]; And it worked for me. – Triangulate

Answer 2

In case you want to write fallback code, decoding from base64 has been present in iOS since the very beginning by caveat of NSURL:

NSURL *URL = [NSURL URLWithString:
      [NSString stringWithFormat:@"data:application/octet-stream;base64,%@",
           base64String]];

return [NSData dataWithContentsOfURL:URL];

Flowery

I'm totally impressed with this answer. For years i've been using some ridiculous amount of code to decode a string, and all along there was a 2 line solution. – Liberty

This is awesome! Hacky, but awesome :) – Denary

I've never thought is is so easy! Thanks!! – Suffer

Answer 3

While decoding the base64String I was getting nil for using:

NSData *decodedData = [[NSData alloc] initWithBase64EncodedString:base64String options:0];

So, I used:

NSData *decodedData = [[NSData alloc] initWithBase64EncodedString:base64String options:NSDataBase64DecodingIgnoreUnknownCharacters];

And it worked for me.

Triangulate