Converting NSData to NSString returns nil

Question

I know this question is asked before, but none of the solutions worked for me. I am trying to convert an NSData object to a NSString value. I am initing the NSString object like following:

NSString *html = [[NSString alloc] initWithData:urlData encoding:NSUTF8StringEncoding];

But the html is always nil. The NSData I am trying to convert is the source code of a website. It is fairly long. This is 'NSData` I am trying to convert.

Is it the length of the data that is causing the issue? I need the source code as a string. What can I do to resolve this issue? What I tried so far:

Tried with all encoding formats as shown in this answer.
Tried with [NSString stringWithUTF8String:[urlData bytes]];

But whatever I do produce the same result. html always is nil whatever I do.

EDIT

It was a problem with the debug console. Even when the objects had values in it, the debug console always showed nil as the value for most of the objects. However NSLog always displays the value.

I would look at the `NSData` object. Add some debugging to check length and disclose some of its content. If these look OK, then encoding is the next suspect. — trojanfoe, Jul 02 '14 at 09:19
Are you sure the NSData object you are using is the one you are logging? Silly question but this is the Internet so I have to ask unless you show. — borrrden, Jul 02 '14 at 09:24
Sorry I didn't get you. I have showed the NSData object in the pastebin link above. — Harikrishnan, Jul 02 '14 at 09:33
I didn't see that initially. I'd say that data looks OK, so it's a strange error. — trojanfoe, Jul 02 '14 at 09:33
@nicael: it is certainly UTF8, please see the content of the data from the pastebin link. — Harikrishnan, Jul 02 '14 at 09:34
@trojanfoe It is certainly UTF8, but still I tried with all possible encoding formats. No success. — Harikrishnan, Jul 02 '14 at 09:35
Questions should be self-contained. What happens when pastebin goes down? Include all relevant data in the question itself. If you have to include 100K of text, then perhaps you need to narrow it down a bit more. — dandan78, Jul 02 '14 at 09:39
@dandan78 The `NSData` object by itself is more that 200K of text. Certainly can't include it here. — Harikrishnan, Jul 02 '14 at 09:42
I got it almost work with the `NSUTF8StringEncoding`. Is that what you should retrieve: http://pastebin.com/qWy99EPy ? — Larme, Jul 02 '14 at 09:48
@Larme Did you use the same code as mine and got it working? — Harikrishnan, Jul 02 '14 at 09:56
Using a synchronous request. `urlData = [NSURLConnection sendSynchronousRequest:mUrlRequest1 returningResponse:&response error:&error];` — Harikrishnan, Jul 02 '14 at 10:21
@HarikrishnanT http://chat.stackoverflow.com/rooms/56637/nsdata-nsstring-issue — Larme, Jul 02 '14 at 10:22

score 2 · Accepted Answer · answered Jul 10 '14 at 12:17

2

It's not a problem with debugger
The problem comes from compiler optimization, compiler see that string was not directly used, and optimizes the code by removing it and directly passing it to another method.

The key of the problem : You are running project on release scheme

Solution:
Here is a small guide to switch project to the Debug scheme

1) Click on the target, and click Edit scheme...

enter image description here

2) Popup will be displayed

enter image description here

3) Click Run %Your project%
4) Open Build Configuration popup
5) Select Debug
5) Press OK
6) You are ready to Go!, now you can debug anything :)

answered Jul 10 '14 at 12:17

l0gg3r

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Hi, I will check this and say as soon as i reach office tomorrow. :) – Harikrishnan Jul 10 '14 at 18:04
You said it.. Thanks.. That was the problem. :) – Harikrishnan Jul 11 '14 at 05:21

score 1 · Answer 2 · answered Jul 02 '14 at 10:14

1

If you are using ARC, and you just wrote the code that converts the data to a string and haven't written any code yet that actually uses the string, it will get deallocated immediately. Check whether that is what is happening. For example, what does NSLog (@"%@", html) display?

answered Jul 02 '14 at 10:14

gnasher729

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Well, I am using the string right on the next line of `NSString *html = [[NSString alloc] initWithData:urlData encoding:NSUTF8StringEncoding];`, that is the allocating code. I tried setting a breakpoint on the line allocation(above line) and stepped into and found that the string is nil even after allocating, right in the next line of allocation. That definitely can't be ARC right? – Harikrishnan Jul 02 '14 at 10:17

score 0 · Answer 3 · answered Jul 02 '14 at 10:18

0

NSAttributedString *str = [[NSAttributedString alloc] initWithData:data options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
NSCharacterEncodingDocumentAttribute: [NSNumber numberWithInt:NSUTF8StringEncoding]}
documentAttributes:nil error:&error];

answered Jul 02 '14 at 10:18

Mahesh

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Even this is returning nil – Harikrishnan Jul 02 '14 at 10:33

score -1 · Answer 4 · answered Jul 02 '14 at 09:39

-1

Try this one:

 NSString *myString = [[NSString alloc] initWithData:urlData encoding:NSASCIIStringEncoding];

Generally, conversion from NSData to NSString returns nil means there is mismatch between encoding format received from server and approach used for encoding.

answered Jul 02 '14 at 09:39

Jayprakash Dubey

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I had already tried this one. Just tried again. Not working. As I said, I tried with ALL encoding types. – Harikrishnan Jul 02 '14 at 09:42
Then there might be issue from response received from server end. Try using another response. – Jayprakash Dubey Jul 02 '14 at 09:47
I have already posted the `NSData` object along with the question. The response looks OK. And rather, it is the response I need to convert to string. Converting another response may work, but certainly won't help me. :) – Harikrishnan Jul 02 '14 at 09:51

Converting NSData to NSString returns nil

4 Answers4