Converting NSData to NSString returns nil

3
votes

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.

4
iosobjective-cnsstringnsdata
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
Is your data encoding is UTF8? – nicael
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
Sorry I didn't get you. I have showed the NSData object in the pastebin link above. – Harikrishnan
I didn't see that initially. I'd say that data looks OK, so it's a strange error. – trojanfoe

4 Answers

2
votes

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 :)

1
votes

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?

0
votes
NSAttributedString *str = [[NSAttributedString alloc] initWithData:data options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
NSCharacterEncodingDocumentAttribute: [NSNumber numberWithInt:NSUTF8StringEncoding]}
documentAttributes:nil error:&error];
-1
votes

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.