Objective-C: Base64 to NSString and NSString to Base64


xcode

While working on the CSCW Lab project, I encountered a situation in which the XML-RPC call returned an image, of course encoded as Base64. And guess what – in its known style, Apple doesn’t provide Base64 encoding and decoding – quite lame, given the fact that this encoding is used everywhere in data transfer over the internet – e-mail, browsers, web services – all of them use at some point this encoding to overcome the different local encodings on each one’s machine.

Once identified this problem, I had to solve it somehow – but guess what? – over the free sources there aren’t too many functions that provide this simple and basic encoding.

Finally, after few hours of searching, I finally found that Eric Czarny had a very successful implementation of this in its Cocoa XML-RPC Framework . After taking a quick look at its code, I end up using and importing into my project the

  • NSStringAdditions.h. NSStringAdditions.m – providing the new category

+ (NSString *)base64StringFromData: (NSData *)data length: (int)length;

  • NSDataAdditions.h and NSDataAdditions providing the new category:

+ (NSData *)base64DataFromString: (NSString *)string;

Being categories, they are automatically added to NSString and NSData automatically at runtime, thus their usage is straight forward :

UIImageView *uiIV;
// currentElementValue holds the string representation of the image, encoded in Base64
NSData *nsD = [NSData base64DataFromString: [dataLayer currentElementValue]];
   
if ([nsD ){
    uiIV = [[UIImageView alloc] initWithImage:[UIImage imageWithData: nsD]];
}

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