I want to search a string with my regex, but my regex doesn't match anything ...
This is the content I have:
<h4>Text</h4>
<p><span>Some text I want to catch</p></span>
<p><span>Some text I want to catch</p></span>
<p><span>Some text I want to catch</p></span>
<h4>Other Text</h4>
<p><span>...<p><span>
...
This is my NSRegularExpression:
NSString *regex = #"<h4>Text</h4>(.*?)<h4>";
NSError *error = nil;
NSRegularExpression *pattern = [NSRegularExpression regularExpressionWithPattern:regex options:0 error:&error];
NSRange rangeOfString = NSMakeRange(0, content.length);
NSArray *matches = [[NSArray alloc] init];
matches = [pattern matchesInString:content options:0 range:rangeOfString];
NSString *matchText;
NSMutableArray *mutableArray = [[NSMutableArray alloc] init];
for (NSTextCheckingResult *match in matches) {
matchText = [content substringWithRange:[match rangeAtIndex:1]];
[mutableArray addObject:matchText];
}
I want to catch the text (with tags) between the two headlines, but my NSArray "matches" / NSMutableArray "mutableArray" is still empty.
My other regex are working ...
I checked this regex in an online regex-evaluator and got my text but in my application this regular expression doesn't work.
Is something wrong with my code or regular expression?
By default, the dot . does not match a line separator.
Since the text that you want to capture spans multiple lines, you have to add the
NSRegularExpressionDotMatchesLineSeparators option:
NSRegularExpression *pattern = [NSRegularExpression regularExpressionWithPattern:regex
options:NSRegularExpressionDotMatchesLineSeparators
error:&error];
Alternatively, add (?s) to the pattern to add the "s" flag.
Related
i need to find usernames (like twitter ones) in strings, for example, if the string is:
"Hello, #username! How are you? And #username2??"
I want to isolate/extract #username and #username2
Do you know how to do it in Objective-C, i found this for Python regex for Twitter username but does not work for me
I tried it like this, but is not working:
NSString *comment = #"Hello, #username! How are you? And #username2??";
NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"(?<=^|(?<=[^a-zA-Z0-9-\\.]))#([A-Za-z]+[A-Za-z0-9-]+)" options:0 error:&error];
NSArray *matches = [regex matchesInString:comment options:0 range:NSMakeRange(0, comment.length)];
for (NSTextCheckingResult *match in matches) {
NSRange wordRange = [match rangeAtIndex:1];
NSString *username = [comment substringWithRange:wordRange];
NSLog(#"searchUsersInComment result --> %#", username);
}
(?<=^|(?<=[^a-zA-Z0-9-\\.]))#([A-Za-z]+[A-Za-z0-9-]+) is to neglect emails and grab only usernames, as your string doesn't contain any emails, you should just use #([A-Za-z]+[A-Za-z0-9-]+)
Your regex is wrong. You need to modify it to:
NSString *comment = #"Hello, #username! How are you? And #username2??";
NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"#([A-Za-z]+[A-Za-z0-9-]+)" options:0 error:&error];
NSArray *matches = [regex matchesInString:comment options:0 range:NSMakeRange(0, comment.length)];
for (NSTextCheckingResult *match in matches) {
NSRange wordRange = [match rangeAtIndex:1];
NSString *username = [comment substringWithRange:wordRange];
NSLog(#"searchUsersInComment result --> %#", username);
}
FYI: Any subpattern inside a pair of parentheses will be captured as a group. In practice, this can be used to extract information like phone numbers or emails from all sorts of data.
Imagine for example that you had a command line tool to list all the image files you have in the cloud. You could then use a pattern such as ^(IMG\d+.png)$ to capture and extract the full filename, but if you only wanted to capture the filename without the extension, you could use the pattern ^(IMG\d+).png$ which only captures the part before the period.
I would suggest you to read about regex strings: http://regexone.com/lesson/capturing_groups
I found a problem in regular expression to match all group repetition.
This is a simple example:
NSString *string = #"A1BA2BA3BC";
NSString *pattern = #"(A[^AB]+B)+C";
NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern options:0 error:&error];
NSArray *array = [regex matchesInString:string options:0 range:NSMakeRange(0, [string length])];
Returning array have one element which contains two ranges, whole input string and last captured group "A3B". First two groups, "A1B" and "A2B", are not captured as I expected.
I've tried all from greedy to lazy matching.
A Quantifier Does not Spawn New Capture Groups
Except in .NET, which has CaptureCollections, adding a quantifier to a capture group does not create more captures. The group number stays the same (in your case, Group 1), and the content returned is the last capture of the group.
Reference
Everything about Regex Capture Groups (see Generating New Capture Groups Automatically)
Iterating the Groups
If you wanted to match all the substrings while still validating that they are in a valid string (composed of such groups and ending in C), you could use:
A[^AB]+B(?=(?:A[^AB]+B)*C)
The whole string, of course, would be
^(?:A[^AB]+B)+C$
To iterate the substrings: something like
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"A[^AB]+B(?=(?:A[^AB]+B)*C)" options:0 error:&error];
NSArray *matches = [regex matchesInString:subject options:0 range:NSMakeRange(0, [subject length])];
NSUInteger matchCount = [matches count];
if (matchCount) {
for (NSUInteger matchIdx = 0; matchIdx < matchCount; matchIdx++) {
NSTextCheckingResult *match = [matches objectAtIndex:matchIdx];
NSRange matchRange = [match range];
NSString *result = [subject substringWithRange:matchRange];
}
}
else { // Nah... No matches.
}
in objective-c I have a string as follows:
CAST(407704969.734560,
I want to extract the digits:
407704969.734560
The code I'm using is this one:
NSString *stringToCheck = #"CAST(407704969.734560,"
NSRange searchedRange = NSMakeRange(0, [stringToCheck length]);
NSString *pattern = #"(?<=CAST\\()(\\d+?.?\\d+?)(?=,)";
NSError *error = nil;
NSRegularExpression* regex = [NSRegularExpression regularExpressionWithPattern:pattern options:0 error:&error];
NSArray* matches = [regex matchesInString:stringToCheck options:0 range: searchedRange];
for (NSTextCheckingResult* match in matches) {
NSString* matchText = [stringToCheck substringWithRange:[match range]];
NSLog(#"match: %#", matchText);
}
I guess the problem is in the regex, seen that I can't find any tutorial about it.
You could try using following regex:
PATTERN
CAST\((\d+?\.?\d+?),
INPUT
CAST(407704969.734560,
OUTPUT
Match 1: CAST(407704969.734560,
Group 1: 407704969.734560
Or if you only need the digits try this:
PATTERN
(?<=CAST\()(\d+?\.?\d+?)(?=,)
INPUT
CAST(407704969.734560,
OUTPUT
Match 1: 407704969.734560
And here you have not long but really nice regex tutorial:
www.codeproject.com
i have a problem and i don't undestand how to do this ( after 6hours or googling)
i'have a string named "filename" containt this text :"Aachen-Merzbrück EDKA\r\r\nVerkehr"
i want to use regex to only get this part "Aachen-Merzbrück EDKA" but i cant....
here my code :
NSString *expression = #"\\w+\\s[A-Z]{4}";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:expression options:NSRegularExpressionCaseInsensitive error:&error];
NSString *noAirportString = [regex stringByReplacingMatchesInString:filename options:0 range:NSMakeRange(0, [filename length]) withTemplate:#""];
EDIT :
this one work good :
\S+\s+[A-Z]{4}
but now, how to get only this "Aachen-Merzbrück" EDKA from "Aachen-Merzbrück EDKA\r\r\nVerkehr"
my regex with NSRegularExpression return me the same string ....
A couple of issues in your question:
No need to match city name characters - there are always weird ones around (hyphens, apostrophes, etc.) You can just match the first "line" in your text with a test for the ICAO code as an extra security.
Using stringByReplacingMatchesInString: you actually remove the airport name (and ICAO code) that you want keep.
stringByReplacingMatchesInString: is a hacky (because it deletes things, so you need to make your regexes "negative") shortcut that sometimes works (I use it myself) but which risks confusing things - and future readers.
Having said that, a few changes will fix it:
NSString *filename = #"Aachen-Merzbrück EDKA\r\r\nVerkehr";
// Match anything from the beginning of the line up to a space and 4 upper case letters.
NSString *expression = #"^.+\\s[A-Z]{4}$";
NSError *error = NULL;
//Make sure ^ and $ match line endings,
//and make it case sensitive (the default) to explicitly
//match the 4 upper case characters of the ICAO code
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:expression options:NSRegularExpressionAnchorsMatchLines error:&error];
NSArray *matches = [regex matchesInString:filename
options:0
range:NSMakeRange(0, [filename length])];
// Check that there _is_ a match before you continue
if (matches.count == 0) {
// Error
}
NSRange airportNameRange = [[matches objectAtIndex: 0] range];
NSString *airportString = [filename substringWithRange: airportNameRange];
Thanks it's good working, but i use this one, it's work better in my case :
NSString *expression = #"\\S+\\s+[A-Z]{4}";
Main problem: ObjC can tell me there were six matches when my pattern is, #"\\b(\\S+)\\b", but when my pattern is #"A b (c) or (d)", it only reports one match, "c".
Solution
Here's a function which returns the capture groups as an NSArray. I'm an Objective C newbie so I suspect there are better ways to do the clunky work than by creating a mutable array and assigning it at the end to an NSArray.
- (NSArray *)regexWithResults:(NSString *)haystack pattern:(NSString *)strPattern
{
NSArray *ar;
ar = [[NSArray alloc] init];
NSError *error = NULL;
NSArray *arTextCheckingResults;
NSMutableArray *arMutable = [[NSMutableArray alloc] init];
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:strPattern
options:NSRegularExpressionSearch error:&error];
arTextCheckingResults = [regex matchesInString:haystack
options:0
range:NSMakeRange(0, [haystack length])];
for (NSTextCheckingResult *ntcr in arTextCheckingResults) {
int captureIndex;
for (captureIndex = 1; captureIndex < ntcr.numberOfRanges; captureIndex++) {
NSString * capture = [haystack substringWithRange:[ntcr rangeAtIndex:captureIndex]];
//NSLog(#"Found '%#'", capture);
[arMutable addObject:capture];
}
}
ar = arMutable;
return ar;
}
Problem
I am accustomed to using parentheses to match capture groups in Perl in a manner like this:
#!/usr/bin/perl -w
use strict;
my $str = "This sentence has words in it.";
if(my ($what, $inner) = ($str =~ /This (\S+) has (\S+) in it/)) {
print "That $what had '$inner' in it.\n";
}
That code will produce:
That sentence had 'words' in it.
But in Objective C, with NSRegularExpression, we get different results. Sample function:
- (void)regexTest:(NSString *)haystack pattern:(NSString *)strPattern
{
NSError *error = NULL;
NSArray *arTextCheckingResults;
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:strPattern
options:NSRegularExpressionSearch
error:&error];
NSUInteger numberOfMatches = [regex numberOfMatchesInString:haystack options:0 range:NSMakeRange(0, [haystack length])];
NSLog(#"Pattern: '%#'", strPattern);
NSLog(#"Search text: '%#'", haystack);
NSLog(#"Number of matches: %lu", numberOfMatches);
arTextCheckingResults = [regex matchesInString:haystack options:0 range:NSMakeRange(0, [haystack length])];
for (NSTextCheckingResult *ntcr in arTextCheckingResults) {
NSString *match = [haystack substringWithRange:[ntcr rangeAtIndex:1]];
NSLog(#"Found string '%#'", match);
}
}
Calls to that test function, and the results show it is able to count the number of words in the string:
NSString *searchText = #"This sentence has words in it.";
[myClass regexTest:searchText pattern:#"\\b(\\S+)\\b"];
Pattern: '\b(\S+)\b'
Search text: 'This sentence has words in it.'
Number of matches: 6
Found string 'This'
Found string 'sentence'
Found string 'has'
Found string 'words'
Found string 'in'
Found string 'it'
But what if the capture groups are explicit, like so?
[myClass regexTest:searchText pattern:#".*This (sentence) has (words) in it.*"];
Result:
Pattern: '.*This (sentence) has (words) in it.*'
Search text: 'This sentence has words in it.'
Number of matches: 1
Found string 'sentence'
Same as above, but with \S+ instead of the actual words:
[myClass regexTest:searchText pattern:#".*This (\\S+) has (\\S+) in it.*"];
Result:
Pattern: '.*This (\S+) has (\S+) in it.*'
Search text: 'This sentence has words in it.'
Number of matches: 1
Found string 'sentence'
How about a wildcard in the middle?
[myClass regexTest:searchText pattern:#"^This (\\S+) .* (\\S+) in it.$"];
Result:
Pattern: '^This (\S+) .* (\S+) in it.$'
Search text: 'This sentence has words in it.'
Number of matches: 1
Found string 'sentence'
References:
NSRegularExpression
NSTextCheckingResult
NSRegularExpression matching options
I think if you change
// returns the range which matched the pattern
NSString *match = [haystack substringWithRange:ntcr.range];
to
// returns the range of the first capture
NSString *match = [haystack substringWithRange:[ntcr rangeAtIndex:1]];
You will get the expected result, for patterns containing a single capture.
See the doc page for NSTextCheckingResult:rangeAtIndex:
A result must have at least one range, but may optionally have more (for example, to represent regular expression capture groups).
Passing rangeAtIndex: the value 0 always returns the value of the the range property. Additional ranges, if any, will have indexes from 1 to numberOfRanges-1.
Change the NSTextCheckingResult:
- (void)regexTest:(NSString *)haystack pattern:(NSString *)strPattern
{
NSError *error = NULL;
NSArray *arTextCheckingResults;
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:strPattern
options:NSRegularExpressionSearch
error:&error];
NSRange stringRange = NSMakeRange(0, [haystack length]);
NSUInteger numberOfMatches = [regex numberOfMatchesInString:haystack
options:0 range:stringRange];
NSLog(#"Number of matches for '%#' in '%#': %u", strPattern, haystack, numberOfMatches);
arTextCheckingResults = [regex matchesInString:haystack options:NSRegularExpressionCaseInsensitive range:stringRange];
for (NSTextCheckingResult *ntcr in arTextCheckingResults) {
NSRange matchRange = [ntcr rangeAtIndex:1];
NSString *match = [haystack substringWithRange:matchRange];
NSLog(#"Found string '%#'", match);
}
}
NSLog output:
Found string 'words'