I'm trying to separate a string by the use of a comma. However I do not want to include commas that are within quoted areas. What is the best way of going about this in Objective-C?
An example of what I am dealing with is:
["someRandomNumber","Some Other Info","This quotes area, has a comma",...]
Any help would be greatly appreciated.
Regular expressions might work well for this, depending on your requirements. For example, if you're always trying to match items that are enclosed in double quotes, then the it might be easier to look for the quotes rather than worrying about the commas.
For example, you could do something like this:
NSString *pattern = #"\"[^\"]*\"";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern
options:NSRegularExpressionCaseInsensitive error:&error];
NSArray *matches = [regex matchesInString:string options:0 range:NSMakeRange(0, [string length])];
for (NSTextCheckingResult *match in matches) {
NSRange matchRange = [match range];
NString *substring = [string substringWithRange:matchRange];
// do whatever you need to do with the substring
}
This code looks for a sequence of characters enclosed in quotes (the regex pattern "[^"]*"). Then for each match it extracts the matched range as a substring.
If that doesn't exactly match your requirements, it shouldn't be too difficult to adapt it to use a different regex pattern.
I'm not in a position to test this code at the moment, so my apologies if there are any errors. Hopefully the basic concept should be clear.
Related
So if I have "7A7F6E88920AB8271A" and I want to split it into an array of strings with same amount of character count, like "7A", "7F", "6E", "88", ... is there any method ready for this, or I have to manually make it on objective C? Thanks.
I am not an objective-c expert, but the following might lead you in the right direction (Regular Expressions)
NSRegularExpression regexp = [NSRegularExpression
regularExpressionWithPattern:#"(\\w){2}"
options:NSRegularExpressionCaseInsensitive error:&error];
NSArray *matches = [regex matchesInString:string options:0
range:NSMakeRange(0, [string length])];
The RegExp (\\w){2}should find all 2-length character words and each of them are in the matches array.
Constructed from examples on this page: https://developer.apple.com/reference/foundation/nsregularexpression
NSString *yourString = #"/Users/user/Downloads/data(1).txt.download/data(1).txt";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#"/Users/user/Downloads/data(1).txt-*\\d*.download"
options:NSRegularExpressionCaseInsensitive
error:&error];
[regex enumerateMatchesInString:yourString options:0 range:NSMakeRange(0, [yourString length]) usingBlock:^(NSTextCheckingResult *match, NSMatchingFlags flags, BOOL *stop){
// your code to handle matches here
NSLog(#"%# %ld",match,flags);
}];
Refer to the code above, when there is special character "(" in the file name, it can not be matched because regularExpression should use "\\(", ofCourse i can use #"/Users/user/Downloads/data\\(1\\).txt-*\\d*.download" to match, but how about when the file name contains other special characters. Is there any way to handle with this scenario in a common way?
The parameter regularExpressionWithPattern should be a variable with [NSString stringWithFormat:xxx]
Is there any way to handle with this scenario in a common way?
Why not solve the problem with a regular expression (RE)? I.e. before using a string which you wish to match as-is as part of a pattern apply a RE to the string which matches any RE metacharacters and add the required escape.
E.g. the pattern [()] will match an open or a close parenthesis and you can replace any match with \\ followed by itself.
HTH
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'm trying to remove any non-alphanumeric character within a string. I tried the following code snippet, but it is not replacing the appropriate character.
NSString *theString = #"\"day's\"";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"^\\B\\W^\\B" options:NSRegularExpressionCaseInsensitive error:&error];
NSString *newString = [regex stringByReplacingMatchesInString:theString options:0 range:NSMakeRange(0, [theString length]) withTemplate:#""];
NSLog(#"the resulting string is %#", newString);
Since there'e a need to preserve the enclosing quotation marks in the string, the regex necessarily becomes a bit complex.
Here is one which does it:
(?:(?<=^")(\W+))|(?:(?!^")(\W+)(?=.))|(?:(\W+)(?="$))
It uses lookbehind and lookahead to match the quotation marks, without including them in the capture group, and hence they will not be deleted in the substitution with the empty string.
The three parts handle the initial quotation mark, all characters in the middle and the last quotation mark, respectively.
It is a bit pedestrian and there has to be a simpler way to do it, but I haven't been able to find it. Others are welcome to chime in!
NSString *theString = #"\"day's\"";
NSString *pattern = #"(?:(?<=^\")(\\W+))|(?:(?!^\")(\\W+)(?=.))|(?:(\\W+)(?=\"$))";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern: pattern
options: 0 // No need to specify case insensitive, \W makes it irrelevant
error: &error];
NSString *newString = [regex stringByReplacingMatchesInString: theString
options: 0
range: NSMakeRange(0, [theString length])
withTemplate: #""];
The (?:) construct creates a non-capturing parenthesis, meaning that you can keep the lookbehind (or lookahead) group and "real" capture group together without creating an actual capture group encapsulating the whole parenthesis. Without that you couldn't just substitute an empty string, or it would all be deleted.
So I have a string:
users/9881570/?access_token=
that I try to match with the regex:
NSRegularExpression * regex = [NSRegularExpression regularExpressionWithPattern:#"users/\\d/?access_token=" options:NSRegularExpressionCaseInsensitive error:&error];
NSArray* wordArray = [regex matchesInString:self.currentRequestURL_
options:0 range:NSMakeRange(0, [self.currentRequestURL_ length])];
However, the wordArray has a count of 0. Why is this not matching?
For one thing, you need to escape the question mark, and for another you need a plus sign (+) after your \d to indicate 1 or more numbers. As it is now you only look for one digit.
#"users/\\d+/\\?access_token="
Because the question mark is a special character in regular expressions, and it needs to be escaped.