Conversion of NSData to NSString fails due to some charecters - iphone

Question

I am converting NSData to NSString which I got as response of a url using the following method.
NSString *result = [[NSString alloc] initWithData:_Data encoding:NSUTF8StringEncoding];
It works fine and I am using this for a long time but today I faced an issue while loading the data (paging) at one page my result gives null string.
So I searched SO and found a method from this link NSData to NSString converstion problem!
[NSString stringWithCString:[theData bytes] length:[theData length]];
and this works fine.
My queries,
The method was deprecated in iOS 2.0. If I use this will I be facing any issue in future?
I think this is the text that made the method fail What is this and is there any way that I can encode this using NSUTF8StringEncoding?
What is the the alternative encoding that I can use for encoding all the type of characters like in the above pic?

Answer 1

In order to obtain the type of the content which is sent by the server, you need to inspect the Content-Type header of the response.
The content type's value specifies a "MIMI type", e.g.:
Content-Type: text/plain
A Content-Type's value may additionally specify a character encoding, e.g.:
Content-Type: text/plain; charset=utf-8
Each MIME type should define a "default" charset, which is to be used when there is no charset parameter specified.
For text/* media types the default charset is US-ASCII.
(see RFC 6657, §3).
The following code snippet demonstrates how to safely encode the body of a response:
- (NSString*) bodyString {
CFStringEncoding cfEncoding = NSASCIIStringEncoding;
NSString* textEncodingName = self.response.textEncodingName;
if (textEncodingName) {
cfEncoding = CFStringConvertIANACharSetNameToEncoding( (__bridge CFStringRef)(textEncodingName) );
}
if (cfEncoding != kCFStringEncodingInvalidId) {
NSStringEncoding encoding = CFStringConvertEncodingToNSStringEncoding(cfEncoding);
return [[NSString alloc] initWithData:self.body encoding:encoding];
}
else {
return [self.body description];
}
}
Note:
body is a property returning a NSData object representing the response data.
response is a property returning the NSHTTPURLResponse object.

Answer 2

If
NSString *result = [[NSString alloc] initWithData:_Data encoding:NSUTF8StringEncoding];
returns nil then _Data does not contain a valid string in UTF-8 encoding.
You said that
[NSString stringWithCString:[theData bytes] length:[theData length]];
works fine in your case. This method
interprets the data bytes in the "default C string encoding", but it is unspecified which
encoding that is (and therefore this method is deprecated and should not be used).
I think the default C string encoding is still "Mac Roman". In that case
NSString *result = [[NSString alloc] initWithData:_Data encoding:NSMacOSRomanStringEncoding];
would be the correct solution. But in any case, you should find out which encoding
the web service uses for the response, and specify that in the initWithData:encoding:
method.

Answer 3

Try this
NSString *theString = [NSString stringWithFormat:#"To be continued%C", ellipsis];
NSData *asciiData = [theString dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *asciiString = [[NSString alloc] initWithData:asciiData encoding:NSASCIIStringEncoding];
NSLog(#"Original: %# (length %d)", theString, [theString length]);
NSLog(#"Converted: %# (length %d)", asciiString, [asciiString length]);

Answer 4

It is due to the uncorrect string encoding.
You can try:
save the NSData to the disk with dataPath
use the NSString class method to create the string:
+ (id)stringWithContentsOfURL:(NSURL *)url usedEncoding:(NSStringEncoding *)enc error:(NSError **)error
Notice here:
enc
Upon return, if url is read successfully, contains the encoding used to interpret the data.
So if the method successes, you can get the correct string and all is done by the iOS.