Cut out a part of a long NSString

Question

In my app I want to show a String that contains news. This string is being loaded just from a free Website, so the plain source code of the website does not contain only my string, its is more os less like this:

Stuff
More Stuff
More HTML Stuff
My String
More HTML Stuff
Final Stuff

And of course i want to cut off all the html stuff that i don't want in my NSString. Since i am going to change the String fron time to time the overall length of the Source code from the website changes. This means that substringFromIndex wont work. Is there any other way to Convert the complete source code to just the String that i need?

See http://stackoverflow.com/questions/422138/regular-expressions-in-an-objective-c-cocoa-application for more information on regex capabilities. — Flyingdiver, Aug 20 '11 at 18:35

SSteve · Accepted Answer · 2011-08-20T22:23:45.680

There are zillions of ways to manipulate text. I would start with regular expressions. If you give more details about the specifics of your problem, you can get more specific help.

Edit

Thanks for the link to the website. That gives me more to work with. If you will always know the id of the div whose contents you want, you can use NSXMLParser to extract the text of the div. This will set the text of an NSTextField to the contents of the div with id "I3_sys_txt". I did this on the Mac but I believe it will work on the iPhone as well.

-(IBAction)buttonPressed:(id)sender {
    captureCharacters = NO;
    NSURL *theURL = [NSURL URLWithString:@"http://maxnerios.yolasite.com/"];
    NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:theURL];
    [parser setDelegate:self];
    [parser parse];
    [parser release];
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict {
    if ([elementName isEqual:@"div"] && [[attributeDict objectForKey:@"id"] isEqual:@"I3_sys_txt"]) {
        captureCharacters = YES;
        divCharacters = [[NSMutableString alloc] initWithCapacity:500];
    }
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
    if (captureCharacters) {
        //from parser:foundCharacters: docs:
        //The parser object may send the delegate several parser:foundCharacters: messages to report the characters of an element. 
        //Because string may be only part of the total character content for the current element, you should append it to the current 
        //accumulation of characters until the element changes.
        [divCharacters appendString:string];
    }
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {
    if (captureCharacters) {
        captureCharacters = NO;
        [textField setStringValue:divCharacters];
        [divCharacters release];
    }
}

What information do you need? The website is this: http://maxnerios.yolasite.com/ i want to display the !!!!!!! in my app in a label. If you look at the source code of the site you will see that there is a lot of code, and somewhere in the middle you will find the !!!!! . If i make my ASIHTTPRequest the complete source code of the website returns. Then i want to cut out the !!!!!'s so that i remove all the html code and I return just the String that you can see on the website — JonasG, Aug 20 '11 at 18:41
could I also use stringByReplacingOccurrencesOfString: to replace first the part before my string with @"" and then the part after my string with @"" ? I can't test any code right now because im away. — JonasG, Aug 21 '11 at 02:10
Once you have the extracted string you can prepend and append anything you want. — SSteve, Aug 21 '11 at 07:00

score 0 · Answer 2 · answered Aug 20 '11 at 22:08

Here is the NSRegularExpression class that you need to use: NSRegularExpression

Here is a 'beginning' tutorial on how to use the class: Tutorial

Here is a primer on what regular expressions are: Regex Primer

Here is an online regular expression tester: Tester

The tester may not work exactly as NSRegularExpression but it will help you understand regex definitions in general. Regular expressions are a key tool for software developers, a little daunting at first, but they can be used to great effect when searching or manipulating strings.

Although this looks like a lot of work - there is no 'quick answer' to what you are attempting. You say "is there any other way to Convert the complete source code to just the String I need?' - the answer is yes - regular expressions. But you need to define what 'just the String that I need' means, and regular expressions are one important way.

Cut out a part of a long NSString

2 Answers2

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