NSRegularExpression:enumerateMatchesInString hangs when called more than once - objective-c

Question

In the context of an iPhone app I am developing, I am parsing some html to extract data to map, using NSRegularExpression. This information is updated whenever the user "pans" the map to a new location.
This works fine the first time or two through, but on the second or third time the function is called, the application hangs. I have used XCode's profiler to confirm I am not leaking memory, and no error is generated (the application does not terminate, it just sits in execution at the point shown below).
When I examine the HTML being parsed, I do not see that it is incomplete or otherwise garbled when the application hangs.
Furthermore, if I replace the regex code with a collection of explicitly address strings, everything works as expected.
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// receivedData contains the returned HTML
NSString *result = [[NSString alloc] initWithData:receivedData encoding:NSASCIIStringEncoding];
NSError *error = nil;
NSString *pattern = #"description.*?h4>(.*?)<\\/h4>.*?\"address>[ \\s]*(.*?)<.*?zip>.*?(\\d{5,5}), US<";
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:pattern
options:NSRegularExpressionDotMatchesLineSeparators
error:&error];
__block NSUInteger counter = 0;
// the application hangs on the next line after 1-2 times through
[regex enumerateMatchesInString:result options:0 range:NSMakeRange(0, [result length]) usingBlock:^(NSTextCheckingResult *match, NSMatchingFlags flags, BOOL *stop){
NSRange range = [match rangeAtIndex:2];
NSString *streetAddress =[result substringWithRange:range];
range = [match rangeAtIndex:3];
NSString *cityStateZip = [result substringWithRange:range];
NSString *address = [NSString stringWithFormat:#"%# %#", streetAddress, cityStateZip];
EKItemInfo *party = [self addItem:address]; // geocode address and then map it
if (++counter > 4) *stop = true;
}];
[receivedData release];
[result release];
[connection release]; //alloc'd previously, so release here.
}
I realize this is going to be difficult/impossible to duplicate, but I was wondering if anyone has run into a similar issue with NSRegularExpression or if there is something obviously wrong here.

Answer 1

I also have encountered the regular expression exception, too. In my case, the problem was Character Encoding. So that I wrote a code to go well with several character encoding. Maybe this code help you.
+ (NSString *)encodedStringWithContentsOfURL:(NSURL *)url
{
// Get the web page HTML
NSData *data = [NSData dataWithContentsOfURL:url];
// response
int enc_arr[] = {
NSUTF8StringEncoding, // UTF-8
NSShiftJISStringEncoding, // Shift_JIS
NSJapaneseEUCStringEncoding, // EUC-JP
NSISO2022JPStringEncoding, // JIS
NSUnicodeStringEncoding, // Unicode
NSASCIIStringEncoding // ASCII
};
NSString *data_str = nil;
int max = sizeof(enc_arr) / sizeof(enc_arr[0]);
for (int i=0; i<max; i++) {
data_str = [
[NSString alloc]
initWithData : data
encoding : enc_arr[i]
];
if (data_str!=nil) {
break;
}
}
return data_str;
}
You can download the whole category library from GitHub and just run it. I wish this helps you.
https://github.com/weed/p120801_CharacterEncodingLibrary

Answer 2

Maybe the answer to this question can be found at: NSRegularExpression enumerateMatchesInString: [...] usingBlock does never stop .
I had this issue solved by passing NSMatchingReportCompletion as option and by setting stop to YES when the match is nil.