How do I convert an NSString value to NSData?

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

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NSString *str = @"helowrld";
// This converts the string to an NSData object
NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];

you can take reference from this link

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Do:

NSData *data = [yourString dataUsingEncoding:NSUTF8StringEncoding];

then feel free to proceed with NSJSONSerialization:JSONObjectWithData.

Correction to the answer regarding the NULL terminator

Following the comments, official documentation, and verifications, this answer was updated regarding the removal of an alleged NULL terminator:

As documented by dataUsingEncoding:: Return Value The result of invoking dataUsingEncoding:allowLossyConversion: with NO as the second argument As documented by getCString:maxLength:encoding: and cStringUsingEncoding:: note that the data returned by dataUsingEncoding:allowLossyConversion: is not a strict C-string since it does not have a NULL terminator

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In case of Swift Developer coming here,

to convert from NSString / String to NSData

var _nsdata = _nsstring.dataUsingEncoding(NSUTF8StringEncoding)

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Objective-C:

NSString *str = @"test string";
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:str];
NSString *thatStr = [NSKeyedUnarchiver unarchiveObjectWithData:data];

Swift:

let str = "test string"
let data = NSKeyedArchiver.archivedData(withRootObject: str)
let thatStr = NSKeyedUnarchiver.unarchiveObject(with: data) as! String

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First off, you should use dataUsingEncoding: instead of going through UTF8String. You only use UTF8String when you need a C string in that encoding.

Then, for UTF-16, just pass NSUnicodeStringEncoding instead of NSUTF8StringEncoding in your dataUsingEncoding: message.

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For Swift 3, you will mostly be converting from String to Data.

let myString = "test"
let myData = myString.data(using: .utf8)
print(myData) // Optional(Data)

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NSString *str = @"hello";
NSData *data = [NSData dataWithBytes:str.UTF8String length:str.length];

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Objective-C:

NSString to NSData:

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

NSData to NSString:

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

Swift:

String to Data:

var testString = "string"
var somedata = testString.data(using: String.Encoding.utf8)

Data to String:

var backToString = String(data: somedata!, encoding: String.Encoding.utf8) as String!

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Update Swift 5.x

let str = "teststring"
let data = str.data(using: .utf8)

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Swift:

Swift 5.x

let myStringToConvert = "My String to Convert in Data"
let myData = str.data(using: .utf8)

String to Data:

var myStringToConvert = "My String to Convert in Data"
var myData = testString.data(using: String.Encoding.utf8)

Data to String:

var backToMyString = String(data: myData!, encoding: String.Encoding.utf8) as String!

OBJECTIVE C:

NSString to NSData :

NSString* myStringToConvert= @"My String to Convert in Data";
NSData* myData=[str dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:NO];

NSData to NSString :

NSString* backToMyString = [[NSString alloc] initWithData: myData encoding:NSUTF8StringEncoding];

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NSString *str = @"Banana";
NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:true];

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Objective-C

NSString *str = @"Hello World";
NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:NO];

Swift

let str = "Hello World"
let data = string.data(using: String.Encoding.utf8, allowLossyConversion: false)

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In Swift there is an API which returns a non-optional

let str = "teststring"
let data = Data(str.utf8)

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