I'm trying to use regexkitlite for string matching in objective-c and I'm having some problems with it. What I'm trying to do is search a large string for substrings matching:
"http://[something].jpg"
"http://[something].png"
Basically, I want to find all links to images from the original string. What I have currently is:
NSString *regexString = #"http://[a-zA-Z0-9._%+-/]+\.jpg";
Now this is working for .jpg images, but of course it doesn't match .png images. I would really like to use one regexString that would match either, but I can't figure out how.
Reading some regex tutorials for other languages, I think it is something along the lines of:
NSString *regexString = #"http://[a-zA-Z0-9._%+-/]+\.(?:jpg|png)";
But I can't quite get it right.
Any help would be greatly appreciated.
You don't need a non-capturing group around the file extensions. It's good practice to use them, but it could be causing an error here. (Does the library support it?)
Also, I simplified your regex slightly by using a predefined character class.
NSString *regexString = #"http://[\w.%+-/]+\.(jpg|png)";
You can see this in action here.
You can also add any file extensions that you want. Ex: (jpg|png|gif|...).
Updated: Apple now includes regular expression support with NSRegularExpression, which is available in OS X v10.7 and later.
Related
I'm trying to run a search within XCode (to find blocks that contain a reference to self though this is not important) however the search is not finding any matches. When I use the same regex expression on various online debuggers or programmatically using NSRegularExpression I get the results I expect. I understand xCode uses the ICU engine, however the documentation for NSRegularExpression states that the ICU syntax is also used.
The expression I am using is as follows (I know its not perfect but it seems to work so far!):
\^\(*[a-zA-z\*\,\s]*\)*[\s]*\{[a-zA-Z0-9:;\[\]\s\=\_\.\/\-#"\!\*\(\)\,]+self
or escaped:
NSString * expression = #"\\^\\(*[a-zA-z\\*\\,\\s]*\\)*[\\s]*\\{[a-zA-Z0-9:;\\[\\]\\s\\=\\_\\.\\/\\-#\"\\!\\*\\(\\)\\,]+self";
Debuggex provides a nice way to visualise the expression and also a test match here Debuggex Demo:
Has any one else come across any quirks with the XCode implementation that might cause false negatives?
Thanks
I am trying to find and process 'java-style' comments within a string in objective-C.
I have a few regex snippets which almost work but I am stuck on one hurdle: different options seem to make the different styles work.
For example, I am using this to match:
NSArray* matches = [[NSRegularExpression regularExpressionWithPattern:expression options:NSRegularExpressionAnchorsMatchLines error:nil] matchesInString:string options:0 range:searchRange];
The options here allow me successfully find and process single line comments (//) but not multiline (/* */), if I change the option to NSRegularExpressionDotMatchesLineSeparators then I can make multiline work fine but I can't find the 'end' of a single line comment.
I suppose really I need dot-matches-line-separators but I need a better way of finding the end of a single line comment?
The regexp I have so far are:
#"/\\*.*?\\*/"
#"//.*$"
it's clear to see if dot matches a line separator then the second one (single line) never 'finishes' but how do I fix this? I found some suggestions for single line that were more like:
#"(\/\/[^"\n\r]*(?:"[^"\n\r]*"[^"\n\r]*)*[\r\n])"
But that doesn't' seem to work at all!
Thanks in advance for any pointers.
So it turns out the example I had was pretty close its just for some reason I had some additional backslashes in there that weren't needed, it now reads:
#"(//[^\"\n\r]*(?:\"[^\"\n\r]*\"[^\"\n\r]*)*[\r\n])"
(that is, in the code for Objective-C). And to clarify my own point, I am using DotMatchesLineSeparator and this is working now exactly as I'd expect.
I have url, for example:
http://i.myhost.com/myimage.jpg
I want to change this url to
http://i.myhost.com/myimageD.jpg.
(Add D after image name and before point)
i.e I want add some words after image name and before point using regex.
What is the best way do it using regex?
Try using ^(.*)\.([a-zA-Z]{3,5}) and replacing with \1D\2. I'm assuming the extension is 3-5 alphanumeric numbers but you can modify it to suit. E.g. if it's just jpg images then you can put that instead of the [a-zA-Z]{3,5}.
Sounds like a homework question given the solution must use a regex, on that assumption here is an outline to get you going.
If all you have is a URL then #mathematical.coffee's solution will suit. However if you have a chunk of text within which is one or more URLs and you have to locate and change just those then you'll need something a little more involved.
Look at the structure of a URL: {protocol}{address}{item}; where
{protocol} is "http://", "ftp://" etc.;
{address} is a name, e.g. "www.google.com", or a number, e.g. "74.125.237.116" - there will always be at least one dot in the address; and
{item} is "/name" where name is quite flexible - there will be zero or more items, you can think of them as directories and a file but this isn't strictly true. Also the sequence of items can end in a "/" (including when there are zero of them).
To make a regex which matches a URL start by matching each part. In the case of the items you'll want to match the last in the sequence separately - you'll have zero or more "directories" and one "file", the latter must be of the form "name.extension".
Once you have regexes for each part you just concatenate them to produce a regex for the whole. To form the replacement pattern you can surround parts of your regex with parentheses and refer to those parts using \number in the replacement string - see #mathematical.coffee's solution for an example.
The best way to learn regexs is to use an editor which supports them and just experiment. The exact syntax may not be the same as NSRegularExpression but they are mostly pretty similar for the basic stuff and you can translate from one to another easily.
I am using RegexKitLite and I'm trying to match a pattern.
The following regex patterns do not capture my word that includes N with a titlde: ñ.
Is there a string conversion I am missing?
subjectString = #"define_añadir";
//regexString = #"^define_(.*)"; //this pattern does not match, so I assume to add the ñ
//regexString = #"^define_([.ñ]*)"; //tried this pattern first with a range
regexString = #"^define_((?:\\w|ñ)*)"; //tried second
NSString *captured= [subjectString stringByMatching:regexString capture:1L];
//I want captured == añadir
Looks like an encoding problem to me. Either you're saving the source code in an encoding that can't handle that character (like ASCII), or the compiler is using the wrong encoding to read the source files. Going back to the original regex, try creating the subject string like this:
subjectString = #"define_a\xC3\xB1adir";
or this:
subjectString = #"define_a\u00F1adir";
If that works, check the encoding of your source code files and make sure it's the same encoding the compiler expects.
EDIT: I've never worked with the iPhone technology stack, but according to this doc you should be using the stringWithUTF8String method to create the NSString, not the #"" literal syntax. In fact, it says you should never use non-ASCII characters (that is, anything not in the range 0x00..0x7F) in your code; that way you never have to worry about the source file's encoding. That's good advice no matter what language or toolset you're using.
Hey guys, given a data set in plain text such as the following:
==Events==
* [[312]] – [[Constantine the Great]] is said to have received his famous [[Battle of Milvian Bridge#Vision of Constantine|Vision of the Cross]].
* [[710]] – [[Saracen]] invasion of [[Sardinia]].
* [[939]] – [[Edmund I of England|Edmund I]] succeeds [[Athelstan of England|Athelstan]] as [[King of England]].
*[[1275]] – Traditional founding of the city of [[Amsterdam]].
*[[1524]] – [[Italian Wars]]: The French troops lay siege to [[Pavia]].
*[[1553]] – Condemned as a [[Heresy|heretic]], [[Michael Servetus]] is [[burned at the stake]] just outside [[Geneva]].
*[[1644]] – [[Second Battle of Newbury]] in the [[English Civil War]].
*[[1682]] – [[Philadelphia]], [[Pennsylvania]] is founded.
I would like to end up with an NSDictionary or other form of collection so that I can have the year (The Number on the left) mapping to the excerpt (The text on the right). So this is what the 'template' is like:
*[[YEAR]] – THE_TEXT
Though I would like the excerpt to be plain text, that is, no wiki markup so no [[ sets. Actually, this could prove difficult with alias links such as [[Edmund I of England|Edmund I]].
I am not all that experienced with regular expressions so I have a few questions. Should I first try to 'beautify' the data? For example, removing the first line which will always be ==Events==, and removing the [[ and ]] occurrences?
Or perhaps a better solution: Should I do this in passes? So for example, the first pass I can separate each line into * [[710]] and [[Saracen]] invasion of [[Sardinia]]. and store them into different NSArrays.
Then go through the first NSArray of years and only get the text within the [[]] (I say text and not number because it can be 530 BC), so * [[710]] becomes 710.
And then for the excerpt NSArray, go through and if an [[some_article|alias]] is found, make it only be [[alias]] somehow, and then remove all of the [[ and ]] sets?
Is this possible? Should I use regular expressions? Are there any ideas you can come up with for regular expressions that might help?
Thanks! I really appreciate it.
EDIT: Sorry for the confusion, but I only want to parse the above data. Assume that that's the only type of markup that I will encounter. I'm not necessarily looking forward to parsing wiki markup in general, unless there is already a pre-existing library which does this. Thanks again!
This code assumes you are using RegexKitLite:
NSString *data = #"* [[312]] – [[Constantine the Great]] is said to have received his famous [[Battle of Milvian Bridge#Vision of Constantine|Vision of the Cross]].\n\
* [[710]] – [[Saracen]] invasion of [[Sardinia]].\n\
* [[939]] – [[Edmund I of England|Edmund I]] succeeds [[Athelstan of England|Athelstan]] as [[King of England]].\n\
*[[1275]] – Traditional founding of the city of [[Amsterdam]].";
NSString *captureRegex = #"(?i)(?:\\* *\\[\\[)([0-9]*)(?:\\]\\] \\– )(.*)";
NSRange captureRange;
NSRange stringRange;
stringRange.location = 0;
stringRange.length = data.length;
do
{
captureRange = [data rangeOfRegex:captureRegex inRange:stringRange];
if ( captureRange.location != NSNotFound )
{
NSString *year = [data stringByMatching:captureRegex options:RKLNoOptions inRange:stringRange capture:1 error:NULL];
NSString *textStuff = [data stringByMatching:captureRegex options:RKLNoOptions inRange:stringRange capture:2 error:NULL];
stringRange.location = captureRange.location + captureRange.length;
stringRange.length = data.length - stringRange.location;
NSLog(#"Year:%#, Stuff:%#", year, textStuff);
}
}
while ( captureRange.location != NSNotFound );
Note that you really need to study up on RegEx's to build these well, but here's what the one I have is saying:
(?i)
Ignore case, I could have left that out since I'm not matching letters.
(?:\* *\[\[)
?: means don't capture this block, I escape * to match it, then there are zero or more spaces (" *") then I escape out two brackets (since brackets are also special characters in a regex).
([0-9]*)
Grab anything that is a number.
(?:\]\] \– )
Here's where we ignore stuff again, basically matching " – ". Note any "\" in the regex, I have to add another one to in the Objective-C string above since "\" is a special character in a string... and yes that means matching a regex escaped single "\" ends up as "\\" in an Obj-C string.
(.*)
Just grab anything else, by default the RegEX engine will stop matching at the end of a line which is why it doesn't just match everything else. You'll have to add code to strip out the [[LINK]] stuff from the text.
The NSRange variables are used to keep matching through the file without re-matching original matches. So to speak.
Don't forget after you add the RegExKitLite class files, you also need to add the special linker flag or you'll get lots of link errors (the RegexKitLite site has installation instructions).
I'm no good with regular expressions, but this sounds like a job for them. I imagine a regex would sort this out for you quite easily.
Have a look at the RegexKitLite library.
If you want to be able to parse Wikitext in general, you have a lot of work to do. Just one complicating factor is templates. How much effort do you want to go to cope with these?
If you're serious about this, you probably should be looking for an existing library which parses Wikitext. A brief look round finds this CPAN library, but I have not used it, so I can't cite it as a personal recommendation.
Alternatively, you might want to take a simpler approach and decide which particular parts of Wikitext you're going to cope with. This might be, for example, links and headings, but not lists. Then you have to focus on each of these and turn the Wikitext into whatever you want that to look like. Yes, regular expressions will help a lot with this bit, so read up on them, and if you have specific problems, come back and ask.
Good luck!