I access a RESTFUL url and get back results. The results are in JSON. I turn the response into a string via:
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
NSString *json = [[NSString alloc] initWithBytes:[self.receivedData mutableBytes] length:[self.receivedData length] encoding:NSUTF8StringEncoding];
The json variable has a value of 0x0. When I mouse over it, I see <Invalid CFStringRef>. How can I debug this to tell why it is invalid? I render the JSON given back through the browser in A JSON parser. That checks out fine.
Results are given back by entering an ID in the URL. Other IDs return results without issue. The result set is fairly large.
First I would use initWithData:encoding: to setup the NSString. Small difference, but that method is there for a reason.
Then, I would do a hexdump of self.receivedData to see what is actually in there. If that data is not properly UTF8 encoded then the initWithData:encoding: will fail.
(Google for NSData hex dump to find other people's utility functions to do this)
I have found that sometimes web services are sloppy with their encoding. So I usually implement a fallback like this:
NSString* html = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
if (html == nil) {
html = [[NSString alloc] initWithData: data encoding: NSISOLatin1StringEncoding];
if (html == nil) {
html = [[NSString alloc] initWithData: data encoding: NSMacOSRomanStringEncoding];
}
}
It is kind of sad that this is required but many web services are not written or configured properly.
Use NSLog to look at the bytes.
Related
I am making a call to get a JSON response like this:
NSData *urlData=[NSURLConnection sendSynchronousRequest:serviceRequest returningResponse:&httpResponse error:nil ];
NSString *returnString=[[NSString alloc]initWithData:urlData encoding:NSUTF8StringEncoding];
However, when I print the string using NSLog:
Emiratos �rabes Unidos
When I convert it to NSData like this:
NSData *jsonData = [returnString dataUsingEncoding:NSUTF8StringEncoding];
NSArray * response = [NSJSONSerialization JSONObjectWithData:jsonData options:0 error:nil];
It turns it to be (when I retrieve the value from the array):
Emiratos \Ufffdrabes Unidos
And when I put it in a label it displays it like this:
Emiratos �rabes Unidos
I would like to display in a label like this:
Emiratos Árabes Unidos
How can I do it?
The problem seems to be this line:
NSString *returnString =
[[NSString alloc] initWithData:urlData
encoding:NSUTF8StringEncoding];
You are assuming that the data is a string encoded as UTF8. But apparently it isn't. Therefore you're seeing the "replacement character" (codepoint U+FFFD) at this point.
You'll need to find out what encoding is actually being used. You can probably just experiment with other encodings. Alternatively, use NSLog to look at the data; an NSData object is logged as a sequence of hex bytes, so by looking at the bytes in that position, and by looking up various encodings on the Internet, you may be able to deduce what encoding is being used here.
(But if you use NSLog and you actually see FFFD at this point, then you've had it; the server itself is supplying the bad data and there's nothing you can do about it, as the good data is lost before you can get at it.)
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?
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.
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.
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]);
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.
I have an app that just opened call a webserver page that gives me a json string.
When I'm on the local network all works without problem but when I open the app outside the local network and without vpn the app crashes.
How can I control the json string?
This is my code:
NSString *urlstr = [[NSString alloc] initWithFormat:#"%#yes.php", av];
NSURL *url = [[NSURL alloc] initWithString:urlstr];
NSError* error = nil;
NSString* urlString = [NSString stringWithContentsOfURL:url encoding:NSASCIIStringEncoding error:&error];
NSString *newStr;
NSData* data=[newStr dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:data
options:kNilOptions
error:&error];
sn1 = [[json objectForKey:#"Rele1"] intValue];
I want to compare the json answer with a NULL value, if the two parameters are equal I show an alert.
EDIT: If I try to read any value, the app crashes waiting the json reply...
I have bypassed the problem with an NSURLRequest with the timeoutInterval parameter that closes the connection after n seconds.
Amongst other things, you fail to:
check whether the attempt to fetch an ASCII-encoded string from a remote URL failed (obvious possibilities: the URL is unreachable, the result is UTF-8 rather than ASCII);
check whether the JSON parsing succeeds (obvious possibility: the server 404d and returned an HTML error page instead)
check whether the returned JSON object was actually a dictionary (eg, it could be an array, in which case calling objectForKey: on it will raise an exception)
The parsing of return data as ASCII then re-encoding into UTF-8 is also probably redundant — because the one supersets the other it has the effect of a threshold test, otherwise preventing acceptable results from proceeding.
Does this code ever worked?
You should check error after [NSString stringWithContentsOfURL:url encoding:NSASCIIStringEncoding error:&error];
you are reading URL data into urlString but then get NSData from uninitialized newStr and parse it?
again you should always check error whenever you provide it before anything else
why do you read the data as ASCII but the NSData as UTF8?
I'm using a JSON file which contains non-English characters.Hence when I'm fetching values from this file, it is showing some Chinese like characters in the simulator.In the console, I'm getting values like
\U2021\U00c6\U00e1\U2021\U00c6\U00a9\U2021\U00d8\U00e7\U2021\U00c6\U00b1\U2021\U00d8
\U00e0\U2021\U00c6\U00d8\U2021\U00c6\U00d6\U2021\U00c6\U2264\U2021\U00c6\U2122\U2021
\U00d8\U00e7\U2021\U00c6\U2122\U2021\U00c6\U00b1\U2021\U00d8\U00e0\U2021\U00c6\U00ef
\U2021\U00d8\U00e7 \U2021\U00c6\U00ef\U2021\U00d8\U00c7\U2021\U00c6\U00fc...
Any idea?
Try to print in such way:
NSString *currentString = [[[NSString alloc] initWithData:characterBuffer encoding:NSUTF8StringEncoding] autorelease];
NSLog(#"Converted string: %#", currentString);
where characterBuffer is buffer where you've collected received data, replace NSUTF8StringEncoding with appropriate encoding, used at your server.
using iphone sdk 4.0. The callback for an http request gives data as an NSData object
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
// Append the data received to our data
[theData appendData:data];
}
In my php script on the server i am returning an array as follows
var_dump($array).
How do i get my array back from the NSMutableData object 'theData' obove on my iphone.
Thanks
You have a string describing your array (or maybe several arrays?) stored as a sequence of bytes in your NSMutableData object. In order to turn it back into an array you're going to need to parse the var_dump output, which is likely to be arduous.
If you can find a library (or roll your own code) to return your data in Apple plist format, your task will be much easier: you can use
[NSPropertyListSerialization propertyListFromData:mutabilityOption:format:errorDescription:]
which takes an NSData (or NSMutableData) pointer as its first argument. Try http://code.google.com/p/cfpropertylist/ for a starting point.
From the example code at the cfpropertylist page:
$plist = new CFPropertyList();
$td = new CFTypeDetector();
$guessedStructure = $td->toCFType( $array );
$plist->add( $guessedStructure );
// and then return the plist content with
$plist->toXML()
and in your iOS code:
NSString *errorString = nil;
NSArray *array = [[NSPropertyListSerialization
propertyListFromData:theData
mutabilityOption:NSPropertyListImmutable
format:nil
errorDescription:&errorString] retain];
I would likely use YAJL on iOS, and $var = json_encode($array); in the PHP. Then in the iOS, I would parse that content from the NSData input like:
YAJLParser *parser = [[YAJLParser alloc] initWithParserOptions:YAJLParserOptionsAllowComments | YAJLParserOptionsCheckUTF8];
parser.delegate = [[[MyArrayParserDelegate alloc] init] autorelease];
[parser parse:data];
NSArray *thePhpArrayReceived = parser.delegate.resultantArray;
Please check out how to structure the delegate, and get YAJL here : Get YAJL + Readme
PHP outputs text so you will have to read that NSData as NSString and then parse out the array data according to the format specified by var_dump. As a starting point, the following code snippet should print out the array (as text) to your console:
NSString * dump = [[NSString alloc] initWithData:theData
encoding:NSUTF8StringEncoding];
NSLog(#"%#", dump);
[dump release];
As Seamus Campbell points out, there are better ways of doing this. Another option would be to output XML from your PHP script, and then use Cocoa's XML parsing methods to retreive the array.