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
Related
How would I do this? I'm new to Objective-C but I can't find anything that would help me do this.
NSArray *splitLine = [currentLine componentsSeparatedByString:#":%#",notNumber];
Where notNumber is a string that represents anything that isn't a number. So I want to separate a string where there are colons separated by strings that aren't numbers. (I want to avoid splitting at times i.e. 3:00pm, but split at iCal parameters like DESCRIPTION: and LOCATION:.)
You can do this in several steps, like this. I have not compiled this code, but it should at least give you an idea of what to do.
1) Create a regex object to match your separators:
NSString *regexString = #"DESCRIPTION:\s|LOCATION:\s"; // or whatever makes sense for your scenario
NSRegularExpression *regex =
[NSRegularExpression regularExpressionWithPattern:regexString
options:NSRegularExpressionCaseInsensitive
error:nil];
2) Replace all the different separators matching your regex with just one separator:
NSRange range = NSMakeRange(0, string.length);
NSString *string2 = [regex stringByReplacingMatchesInString:string
options:0
range:range
withTemplate:#"SEPARATOR"];
3) Split the string!
NSArray *elements = [string2 componentsSeparatedByString:#"SEPARATOR"];
Shortest solution for splitting string.
NSString *str = #"Please split me to form array of words";
NSArray *wordsArray = [str componentsSeparatedByString:#" "];
You can use regular expressions!
Using the pattern (I believe this is the core of your question):
pattern = #"(?<=[^0-9]):(?=[^0-9])"
This pattern will only match ':' symbols not surrounded by numbers.
Then replace with a dummy value that won't show in your data
dummy = #"NEVERSEETHIS"
NSRegularExpressions *regex = [NSRegularExpression regularExpressionWithPattern:pattern options:0 error:nil];
NSRange range = NSMakeRange(0, [string length])
NSString *modified= [regex replaceMatchesInString:yourString options:0 range:range withTemplate:dummy];
and finally, split
return [modified componentsSeparatedByString:dummy];
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.
}
I'm trying to parse the string in the folowing format using the regex:
"Key" = "Value";
The following code is used to extract the "key" and "value":
NSString* pattern = #"([\"\"'])(?:(?=(\\\\?))\\2.)*?\\1";
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern
options:0
error:NULL];
NSRange matchRange = NSMakeRange(0, line.length);
NSTextCheckingResult *match = [regex firstMatchInString:line options:0 range:matchRange];
NSRange rangeKeyMatch = [match rangeAtIndex:0];
matchRange.location = rangeKeyMatch.length;
matchRange.length = line.length - rangeKeyMatch.length;
NSTextCheckingResult *match2 = [regex firstMatchInString:line options:0 range:matchRange];
NSRange rangeValueMatch = [match2 rangeAtIndex:0];
It doesn't look efficient and is not considering the following example as invalid:
"key" = "value" = "something else";
Is there any efficient way to perform parse of this kind of parsing?
I'm not familiar with that dialect, but since you've tagged regex, here's one that should do it in principle: ^"([^"]*)" = "([^"]*)";$
You're not being exact about the format so you may need to add some conditional white-space here and there depending on your input format. Another thing that might come into play is the need to escape the parentheses.
For example with sed, you'd have to write:
echo '"Key" = "Value";' | sed -e 's#^"\([^"]*\)" = "\([^"]*\)";$#key is \1 and value is \2#'
This code should match "key" = "value" and not "key" = "value" = "something else":
NSString *line = #"\"key\" = \"value\"";
NSError *error = NULL;
NSString *pattern = #"\\\"(\\w+)\\\"\\s=\\s\\\"(\\w+)\\\"$";
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern
options:NSRegularExpressionAnchorsMatchLines error:&error];
NSRange matchRange = NSMakeRange(0, line.length);
NSTextCheckingResult *match = [regex firstMatchInString:line options:0 range:matchRange];
/* It looks like you were not quite looking at the ranges properly. The rangeAtIndex 0 is actually the entire string. */
NSRange rangeKeyMatch = [match rangeAtIndex:1];
NSRange rangeValueMatch = [match rangeAtIndex:2];
NSLog(#"Key: %#, Value: %#", [line substringWithRange:rangeKeyMatch], [line substringWithRange:rangeValueMatch]);
I have a string like below.
<br><br><br><br><br> SomeHtmlString <br><br><br><br><br>
I want to remove br tags like trim function preserving middle br tags in SomeHtmlString.
Is there any function to do this shortly?
e.g.
<br><br><br>test1<br><br>test2<br><br><br><br>
to
test1<br><br>test2
Here is a method using regular expressions. It matches only one at a time and replaces that either at the beginning of end of the string.
NSMutableString *replaceMe = [[NSMutableString alloc ]
initWithString:#"<br><br > <br > test<br>test2<br><br>"];
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#"^ *<br *> *"
options:NSRegularExpressionCaseInsensitive
error:&error];
do {
;
} while ([regex replaceMatchesInString:replaceMe options:NSMatchingCompleted range:NSMakeRange(0, replaceMe.length) withTemplate:#""] != 0);
regex = [NSRegularExpression
regularExpressionWithPattern:#" *<br *> *$"
options:NSRegularExpressionCaseInsensitive
error:&error];
do {
;
} while ([regex replaceMatchesInString:replaceMe options:NSMatchingCompleted range:NSMakeRange(0, replaceMe.length) withTemplate:#""] != 0);
NSLog(#"string=%#", replaceMe);
and that does strip "<br><br > <br > test<br>test2<br><br>" down to test<br>test2.
It's probably not the neatest solution but it is very easy to modify to match different expressions, with different whitespace, for example.
It's also possible to use the regular expressions to match several <br>s in one go:
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#"^ *(<br *> *)+"
options:NSRegularExpressionCaseInsensitive
error:&error];
[regex replaceMatchesInString:replaceMe options:NSMatchingCompleted range:NSMakeRange(0, replaceMe.length) withTemplate:#""];
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#" *(<br *> *)+$"
options:NSRegularExpressionCaseInsensitive
error:&error];
[regex replaceMatchesInString:replaceMe options:NSMatchingCompleted range:NSMakeRange(0, replaceMe.length) withTemplate:#""];
which avoids the looping but is a little harder to modify.
You can do this:
NSString* htmlString= #"<br><br><br><br><br> SomeHtmlString <br><br><br><br><br>";
NSString* pureString= [htmlString stringByReplacingOccurrencesOfString: #"<br>" withString: #""];
So you'll have #" SomeHtmlString " in pureString.
You could use this to strip out the unwanted bits:
[yourString stringByReplacingOccurrencesOfString:#"<br>" withString:#""];
Then you would use something like this to remake your string the way you want it:
NSString *newString = [NSString stringWithFormat:#"<br>%#<br>", yourString];
You might also want to look at stringByTrimmingCharactersInSet:
There are so many things you can do with NSString. Check out the Class Reference: https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html
EDIT:
substringToIndex: could be your friend here. You can do this to find out if the first 4 characters of your string consist of the characters you want to remove:
NSString *subString = [yourString substringToIndex:4];
if ([subString isEqualToString:#"<br>"]) {
yourString = [yourString substringFromIndex:4];
}
Then you are creating a new string without those 4 characters. You keep doing this until the first 4 character are not equal to the ones you want to remove.
You can do something similar at the end of your string using substringFromIndex. You will need to know the length of your original string to make sure none of your substrings go out of bounds.
Alternative regular expression rendition:
NSString *input = #"<br><br><br><br><br><br>test<br>test2<br><br><br><br><br><br><br><br><br><br>";
__block NSString *output;
NSError *error;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"^(<br>)*(.*?)(<br>)*$"
options:NSRegularExpressionCaseInsensitive
error:&error];
[regex enumerateMatchesInString:input
options:0
range:NSMakeRange(0, [input length])
usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
NSRange matchRange = [result rangeAtIndex:2];
output = [input substringWithRange:matchRange];
}];
if (output)
NSLog(#"Found: %#", output);
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'