Web Search & Regular Expression Example

By Hawkee on Mar 07, 2009

This code will search the Snippets section of Hawkee.com and return a list of matching snippets on your iPhone. It demonstrates how to retrieve data from a URL and parse it using a regular expression.


This expands on a very basic Cocoa Touch example by Matt Long:


First complete his instructions. He's got a video that makes the process very clear.

After you've completed his tutorial you need to go to Basic_iPhone_AppAppDelegate.h and add a UIWebView for the search results:

IBOutlet UIWebView *web;

Feel free to remove the Label as it isn't necessary for this example.

Next you need to return to the Interface Builder by double clicking MainWindow.xib under Resources. Here you can delete the Label and drag a UIWebView into place as seen here:


Be sure to connect it to your "web" IBOutlet with a control click as you did in the original tutorial.

Next you'll need to download and include the RegexKitLite library. Add RegexKitLite.h and RegexKitLite.m to your Classes folder and follow these steps to add a linker flag to make the library work properly:

Project > Edit Active Target
Select the "Build" tab
Find "Other Linker Flags"
Add "-licucore" to the value column

Finally use the following snippet to replace the "click" IBAction you created in the example code:

- (IBAction)click:(id)sender;
    // Appends the textField search query to the search URL and gets the resulting HTML
    NSString *searchTerm = [textField text];
    NSMutableString *hawkeeURL = [[NSMutableString alloc] initWithString:@"http://www.hawkee.com/snippets/?search_query="];
    [hawkeeURL appendString:searchTerm];
    NSURL *url = [[NSURL alloc] initWithString:hawkeeURL];
    NSString *result = [[NSString alloc] initWithContentsOfURL:url];

    // This will contain the HTML we build from parsing the resulting HTML
    NSMutableString *page = [[NSMutableString alloc] initWithString:@"<span style='font-size: 30px;'>"];

    // Regular expression to match the link to the snippet
    NSString *regexString  = @"<a href='(.+)' class='large'>(.+)</a>";

    // Set these to empty values at first
    NSRange   matchedRange = NSMakeRange(NSNotFound, 0);
    NSError  *error        = NULL;

    // Determine the length of the HTML and search within that range
    int length=[result length];
    NSRange searchRange = NSMakeRange(0, length);

    // done is true when the matchedRange it beyond the length of the result
    Boolean done = false;
        matchedRange = [result rangeOfRegex:regexString options:RKLNoOptions inRange:searchRange capture:1 error:&error];

        // Make sure we found a match within the length of the document
        if(NSMaxRange(matchedRange) <= length)
            // Grab the first match which is the URL
            NSString *snippetURL = [result substringWithRange:matchedRange];

            // Grab the second match which is the snippet name
            matchedRange = [result rangeOfRegex:regexString options:RKLNoOptions inRange:searchRange capture:2 error:&error];
            NSString *snippetName = [result substringWithRange:matchedRange];

            // Build a link to append to the resulting HTML page.
            [page appendString:@"<a href='http://www.hawkee.com"];
            [page appendString:snippetURL];
            [page appendString:@"'>"];
            [page appendString:snippetName];
            [page appendString:@"</a><br><br>\n"];

            // Now start a new range after the previous match that goes to the length of the page.
            searchRange = NSMakeRange(NSMaxRange(matchedRange), length - NSMaxRange(matchedRange));
        else done = true;
    [page appendString:@"</span>"];

    [web loadHTMLString:page baseURL:nil];

    [hawkeeURL release];
    [url release];
    [result release];
    [page release];



Sign in to comment.
Hawkee   -  Nov 28, 2009

sftriman, I imagine as long as the UITextField is declared in a global space it should be available. I didn't get into scope too much with this example though so it's hard to say why it isn't working for you.

sftriman   -  Nov 28, 2009

I'd like to have the search box in one view, then after the search term or phrase is entered, to display the results in another view. I'm having trouble keeping my UITextField *searchTextField object available when I go to the results view I've created. Can you show an example of your code where you split it into a search view and a results view? Thanks!

tv3636   -  Aug 10, 2009

Thanks for this! I just started on my 2nd app.. (first is in review and probably will be for another week at least, but I'll post an image if/when it gets approved) ...and I wanted to use regex but when I added the regexkitlite.h and .m files I got 13 errors, figured I did something wrong and almost gave up. Then I remembered you had a snippet posted and your walkthrough at the end saved me, thanks!

guest598594   -  May 27, 2009
Jamiie   -  May 27, 2009

This work for the 2nd gen ipod touch?

tyagi.anuj   -  Apr 23, 2009

No.... I tried to put both the statements in comment also...(I know it was silly...) Application terminated because of unknown exception. I am trying to figure it out... The errors and warnings are about incompatible types.......

Hawkee   -  Apr 23, 2009

Maybe just try options:0 as that's really what RKLNoOptions represents.

tyagi.anuj   -  Apr 23, 2009

Followed all the steps as it is..... Did not go through the procedure I followed earlier... still getting the same errors..... Both the errors are in the matchedRange = .... statements. :(.

Didn't any one else get such errors???

Hawkee   -  Apr 23, 2009

That's the version I got, so it should work. I think all I did for RegexKitLite was add those 4 files and add the -licucore value under "Other Linker Flags".

tyagi.anuj   -  Apr 22, 2009

I am using Xcode Version 3.1.2

Hawkee   -  Apr 22, 2009

Hmm, what version of Xcode are you using? Maybe this is a problem with the newer version.

tyagi.anuj   -  Apr 22, 2009

I included the RegexKitLite.h/.m file..... I didnt include the RKLMatchEnumerator.h/.m . I did that. It is still giving the same errors. I cleaned the Targets and rebuild the code... Still the same errors....

Just to tell you I went through documentation for RegexKit framework and saw how to connect it and did those steps to like copying it in the target/link Binaries... Was I supposed to do that???

Thanks for such a fast reply. Appreciate it. :)

Hawkee   -  Apr 22, 2009

Did you add RegexKitLite? RKLNoOptions is defined in RegexKitLite.h

tyagi.anuj   -  Apr 22, 2009

Hi. Thank for the tutorial... i am getting two errors in this code one is

..../WebSearchAppDelegate.m:48: error: 'RKLNoOptions' undeclared (first use in this function)
..../WebSearchAppDelegate.m:48: warning: 'NSString' may not respond to '-rangeOfRegex:options:inRange:capture:error:'
..../WebSearchAppDelegate.m:48: warning: (Messages without a matching method signature

..../WebSearchAppDelegate.m:48: error: incompatible types in assignment
..../WebSearchAppDelegate.m:57: warning: 'NSString' may not respond to '-rangeOfRegex:options:inRange:capture:error:'

..../WebSearchAppDelegate.m:57: error: incompatible types in assignment

Did anyone try this code???? Is it working for you guys....

Please help me.... It will help me in my project a lot.....

Thanks again for the tutorial..... :)

Jonesy44   -  Mar 16, 2009

I'm borrowing my friends mac very soon! can't wait to get onto the SDK and get going! :D

adamn   -  Mar 07, 2009

this is the best way for me to learn a new language. i really appreciate you posting this.

as far as which phone is better, i'll stick with the iphone for now. heard a lot of bad things about the storm but it's supposedly better after firmware upgrades. it's a bummer that the g1 doesn't have multi touch, but how often is it really used? zooming in on images, maps, websites, blah. hopefully android will be on an att phone soon. then again, i may switch to verizon if a better phone comes their way.

irchainscriptz   -  Mar 07, 2009

Wow kool, But as a hear from various ppl...Iphone is ok but really not what a lot thought it would be!! I'll stick to my samsung jack until the storm is out ..!!

Aucun50   -  Mar 07, 2009

That looks nice wish i has a iphone :(

Hawkee   -  Mar 07, 2009

Yes, I just posted about that on my profile.

Kirby   -  Mar 07, 2009

This is irrelevant, sorry, but is it me or did Hawkee's snippet "style" change?

Hawkee   -  Mar 07, 2009

Now you just need OS X and Xcode and you'll be ready to go.

Kirby   -  Mar 07, 2009

Wow, this is very neat.

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