How can I convert NSDictionary to NSData and vice versa?

Question

I am sending NSString and UIImage using bluetooth. I decided to store both in a NSDictionary and then convert the dictionary to NSData.

My question is how to convert NSDictionary to NSData and visa versa?

score 369 · Accepted Answer · edited Nov 05 '13 at 15:54

369

NSDictionary -> NSData:

NSData *myData = [NSKeyedArchiver archivedDataWithRootObject:myDictionary];

NSData -> NSDictionary:

NSDictionary *myDictionary = (NSDictionary*) [NSKeyedUnarchiver unarchiveObjectWithData:myData];

edited Nov 05 '13 at 15:54

KIDdAe

2,714
2
22
29

answered Feb 18 '13 at 05:52

Anh Nguyen

5,245
1
20
18

For NSData -> NSDictionary, the cast to NSDictionary seems unnecessary. – Pang Dec 30 '15 at 08:11

score 52 · Answer 2 · edited Nov 03 '16 at 15:56

NSDictionary -> NSData:

NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:yourDictionary forKey:@"Some Key Value"];
[archiver finishEncoding];
[archiver release];

// Here, data holds the serialized version of your dictionary
// do what you need to do with it before you:
[data release];

NSData -> NSDictionary

NSData *data = [[NSMutableData alloc] initWithContentsOfFile:[self dataFilePath]];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
NSDictionary *myDictionary = [[unarchiver decodeObjectForKey:@"Some Key Value"] retain];
[unarchiver finishDecoding];
[unarchiver release];
[data release];

You can do that with any class that conforms to NSCoding.

source

Not to take anything away from this answer, but just a heads that it isn't ARC compliant — Madbreaks, Feb 18 '14 at 19:45

score 46 · Answer 3 · edited Aug 30 '17 at 11:06

Use NSJSONSerialization:

NSDictionary *dict;
NSData *dataFromDict = [NSJSONSerialization dataWithJSONObject:dict
                                                       options:NSJSONWritingPrettyPrinted
                                                         error:&error];

NSDictionary *dictFromData = [NSJSONSerialization JSONObjectWithData:dataFromDict
                                                             options:NSJSONReadingAllowFragments
                                                               error:&error];

The latest returns id, so its a good idea to check the returned object type after you cast (here i casted to NSDictionary).

Luca Davanzo · Answer 4 · 2016-11-03T15:53:48.783

24

In Swift 2 you can do it in this way:

var dictionary: NSDictionary = ...

/* NSDictionary to NSData */
let data = NSKeyedArchiver.archivedDataWithRootObject(dictionary)

/* NSData to NSDictionary */
let unarchivedDictionary = NSKeyedUnarchiver.unarchiveObjectWithData(data!) as! NSDictionary

In Swift 3:

/* NSDictionary to NSData */
let data = NSKeyedArchiver.archivedData(withRootObject: dictionary)

/* NSData to NSDictionary */
let unarchivedDictionary = NSKeyedUnarchiver.unarchiveObject(with: data)

edited Nov 03 '16 at 15:53

answered Jun 12 '15 at 11:28

Luca Davanzo

21,000
15
120
146

Did not work ! Swift 3 equivalent code did not work. let data = NSKeyedArchiver.archivedData(withRootObject: dataFromNetwork) [_SwiftValue encodeWithCoder:]: unrecognized selector sent to instance ... – mythicalcoder Nov 03 '16 at 14:46
Appreciate your quick response. What I meant is this - Swift 3 code also did not work. My data is from 3lvis/networking HTTP library, it is of `Any?` type. But it showed error converting from `NSDictionary` to `NSData`. So I tried your code. It did not work. – mythicalcoder Nov 03 '16 at 15:50

score 19 · Answer 5 · answered Apr 01 '11 at 12:05

19

NSDictionary from NSData

http://www.cocoanetics.com/2009/09/nsdictionary-from-nsdata/

NSDictionary to NSData

You can use NSPropertyListSerialization class for that. Have a look at its method:

+ (NSData *)dataFromPropertyList:(id)plist format:(NSPropertyListFormat)format
                              errorDescription:(NSString **)errorString

Returns an NSData object containing a given property list in a specified format.

answered Apr 01 '11 at 12:05

Jhaliya - Praveen Sharma

31,697
9
72
76

This is a very elegant solution for most Mac OS developers. – mjl007 Mar 27 '18 at 23:31

score 0 · Answer 6 · edited Mar 23 '17 at 03:49

0

Please try this one

NSError *error;
NSDictionary *responseJson = [NSJSONSerialization JSONObjectWithData:webData
                                options:NSJSONReadingMutableContainers
                                error:&error];

edited Mar 23 '17 at 03:49

Alex Zavatone

4,106
36
54

answered May 05 '16 at 13:28

Vijay Kachhadiya

366
2
11

It's `response`, not `responce`. I corrected this for you. – Alex Zavatone Mar 22 '17 at 21:48

How can I convert NSDictionary to NSData and vice versa?

6 Answers6

Linked