Show Menu

Looking to hire an app developer?

Submit your 30 day Job Listing for FREE

There maybe a time that you need to convert the value of an NSString to NSData.

Please Note that this tutorial requires that you have a beginners knowledge of objective-c

This is achieved rather easily. Simply:

NSString* str = @"teststring";
NSData* data = [str dataUsingEncoding:NSUTF8StringEncoding];

Please bear in mind that converting NSString like so will force a trailing \0 byte, which means NSJSONSerialization:JSONObjectWithData and others will fail unless you remove it, so just do this:

data = [data subdataWithRange:NSMakeRange(0, [data length] - 1)];

Then you may proceed to: NSJSONSerialization:JSONObjectWithData

Converting NSData to NSString

If the data is not null-terminated, you should use -initWithData:encoding:

NSString* newStr = [[[NSString alloc] initWithData:theData
                                         encoding:NSUTF8StringEncoding] autorelease];

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: If you have ARC enabled, remove the -autorelease call.

Its, important to keep a note of the Encoding supported by NSString, these are:

enum {
    NSASCIIStringEncoding = 1,      /* 0..127 only */
    NSNEXTSTEPStringEncoding = 2,
    NSJapaneseEUCStringEncoding = 3,
    NSUTF8StringEncoding = 4,
    NSISOLatin1StringEncoding = 5,
    NSSymbolStringEncoding = 6,
    NSNonLossyASCIIStringEncoding = 7,
    NSShiftJISStringEncoding = 8,          /* kCFStringEncodingDOSJapanese */
    NSISOLatin2StringEncoding = 9,
    NSUnicodeStringEncoding = 10,
    NSWindowsCP1251StringEncoding = 11,    /* Cyrillic; same as AdobeStandardCyrillic */
    NSWindowsCP1252StringEncoding = 12,    /* WinLatin1 */
    NSWindowsCP1253StringEncoding = 13,    /* Greek */
    NSWindowsCP1254StringEncoding = 14,    /* Turkish */
    NSWindowsCP1250StringEncoding = 15,    /* WinLatin2 */
    NSISO2022JPStringEncoding = 21,        /* ISO 2022 Japanese encoding for e-mail */
    NSMacOSRomanStringEncoding = 30,
    NSUTF16StringEncoding = NSUnicodeStringEncoding,      /* An alias for NSUnicodeStringEncoding */
    NSUTF16BigEndianStringEncoding = 0x90000100,          /* NSUTF16StringEncoding encoding with explicit endianness specified */
    NSUTF16LittleEndianStringEncoding = 0x94000100,       /* NSUTF16StringEncoding encoding with explicit endianness specified */
    NSUTF32StringEncoding = 0x8c000100,                   
    NSUTF32BigEndianStringEncoding = 0x98000100,          /* NSUTF32StringEncoding encoding with explicit endianness specified */
    NSUTF32LittleEndianStringEncoding = 0x9c000100        /* NSUTF32StringEncoding encoding with explicit endianness specified */

NSASCIIStringEncoding is used to convert ASCII data. NSUTF8StringEncoding is used to convert UTF-8 data.

having issues?

We have a Questions and Answer section where you can ask your iOS Development questions to thousands of iOS Developers.

Ask Question

FREE Download!

Get your FREE Swift 2 Cheat Sheet and quick reference guide PDF download when you sign up to SwiftMonthly

Sharing is caring

If you enjoyed this tutorial, please help us and others by sharing using one of the social media buttons below.

Written by:

I work in the shadows. You can thank me by being a good soul.