Detect Hash Tags #, Mention Tags @, in iOS Like in Twitter App

Detect hash tags #, mention tags @, in iOS like in Twitter App

-(NSMutableAttributedString*)decorateTags:(NSString *)stringWithTags{

    NSError *error = nil;

    //For "Vijay #Apple Dev"
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"#(\\w+)" options:0 error:&error];

    //For "Vijay @Apple Dev"
    //NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"@(\\w+)" options:0 error:&error];

    NSArray *matches = [regex matchesInString:stringWithTags options:0 range:NSMakeRange(0, stringWithTags.length)];
    NSMutableAttributedString *attString=[[NSMutableAttributedString alloc] initWithString:stringWithTags];

    NSInteger stringLength=[stringWithTags length];

    for (NSTextCheckingResult *match in matches) {

        NSRange wordRange = [match rangeAtIndex:1];

        NSString* word = [stringWithTags substringWithRange:wordRange];

        //Set Font
        UIFont *font=[UIFont fontWithName:@"Helvetica-Bold" size:15.0f];
        [attString addAttribute:NSFontAttributeName value:font range:NSMakeRange(0, stringLength)];

        //Set Background Color
        UIColor *backgroundColor=[UIColor orangeColor];
        [attString addAttribute:NSBackgroundColorAttributeName value:backgroundColor range:wordRange];

        //Set Foreground Color
        UIColor *foregroundColor=[UIColor blueColor];
        [attString addAttribute:NSForegroundColorAttributeName value:foregroundColor range:wordRange];

        NSLog(@"Found tag %@", word);

    }

    // Set up your text field or label to show up the result

    //    yourTextField.attributedText = attString;
    //
    //    yourLabel.attributedText = attString;

    return attString;
}

How to make UITextView detect hashtags?

This should work for you

1. Create a new swift file with any name(UITextViewHashtagExtension.swift)

2. Insert this code below:

   import UIKit
   
   extension UITextView {
   
   func resolveHashTags(){
   
       // turn string in to NSString
       let nsText:NSString = self.text
   
       // this needs to be an array of NSString.  String does not work.
       let words:[NSString] = nsText.componentsSeparatedByString(" ")
   
       // you can't set the font size in the storyboard anymore, since it gets overridden here.
       let attrs = [
           NSFontAttributeName : UIFont.systemFontOfSize(17.0)
       ]
   
       // you can staple URLs onto attributed strings
       let attrString = NSMutableAttributedString(string: nsText as String, attributes:attrs)
   
       // tag each word if it has a hashtag
       for word in words {
   
           // found a word that is prepended by a hashtag!
           // homework for you: implement @mentions here too.
           if word.hasPrefix("#") {
   
               // a range is the character position, followed by how many characters are in the word.
               // we need this because we staple the "href" to this range.
               let matchRange:NSRange = nsText.rangeOfString(word as String)
   
               // convert the word from NSString to String
               // this allows us to call "dropFirst" to remove the hashtag
               var stringifiedWord:String = word as String
   
               // drop the hashtag
               stringifiedWord = String(stringifiedWord.characters.dropFirst())
   
               // check to see if the hashtag has numbers.
               // ribl is "#1" shouldn't be considered a hashtag.
               let digits = NSCharacterSet.decimalDigitCharacterSet()
   
               if let numbersExist = stringifiedWord.rangeOfCharacterFromSet(digits) {
                   // hashtag contains a number, like "#1"
                   // so don't make it clickable
               } else {
                   // set a link for when the user clicks on this word.
                   // it's not enough to use the word "hash", but you need the url scheme syntax "hash://"
                   // note:  since it's a URL now, the color is set to the project's tint color
                   attrString.addAttribute(NSLinkAttributeName, value: "hash:\(stringifiedWord)", range: matchRange)
               }
   
           }
       }
   
       // we're used to textView.text
       // but here we use textView.attributedText
       // again, this will also wipe out any fonts and colors from the storyboard,
       // so remember to re-add them in the attrs dictionary above
       self.attributedText = attrString
   }
   
   }
   

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To use this you can do something like this:

self.textView.text = "This is an #example test"
self.textView.resolveHashTags()

---

Updated for Swift 4.0:

extension UITextView {

    func resolveHashTags() {

        // turn string in to NSString
        let nsText = NSString(string: self.text)

        // this needs to be an array of NSString.  String does not work.
        let words = nsText.components(separatedBy: CharacterSet(charactersIn: "#ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_").inverted)

        // you can staple URLs onto attributed strings
        let attrString = NSMutableAttributedString()
        attrString.setAttributedString(self.attributedText)

        // tag each word if it has a hashtag
        for word in words {
            if word.count < 3 {
                continue
            }

            // found a word that is prepended by a hashtag!
            // homework for you: implement @mentions here too.
            if word.hasPrefix("#") {

                // a range is the character position, followed by how many characters are in the word.
                // we need this because we staple the "href" to this range.
                let matchRange:NSRange = nsText.range(of: word as String)

                // drop the hashtag
                let stringifiedWord = word.dropFirst()
                if let firstChar = stringifiedWord.unicodeScalars.first, NSCharacterSet.decimalDigits.contains(firstChar) {
                    // hashtag contains a number, like "#1"
                    // so don't make it clickable
                } else {
                    // set a link for when the user clicks on this word.
                    // it's not enough to use the word "hash", but you need the url scheme syntax "hash://"
                    // note:  since it's a URL now, the color is set to the project's tint color
                    attrString.addAttribute(NSAttributedStringKey.link, value: "hash:\(stringifiedWord)", range: matchRange)
                }

            }
        }

        // we're used to textView.text
        // but here we use textView.attributedText
        // again, this will also wipe out any fonts and colors from the storyboard,
        // so remember to re-add them in the attrs dictionary above
        self.attributedText = attrString
    }
}

Check if string contains a hashtag and then change hashtag color

NSString *tweet = @"This is a tweet #MYTWEET";

NSArray *words = [tweet componentsSeparatedByString:@" "];

NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:tweet];

for (NSString *word in words) {

    if ([word hasPrefix:@"#"]) {

        // Colour your 'word' here
        NSRange matchRange = [tweet rangeOfString:word];

        [attrString addAttribute:kCTForegroundColorAttributeName 
                           value:[UIColor redColor] 
                           range:matchRange]; 
        // Remember to import CoreText framework (the constant is defined there)

    }
}

//Display your attributed string ...

Note: If you're wondering how to display the string, here is one nice open source project : https://github.com/AliSoftware/OHAttributedLabel

How do you detect words that start with “@” or “#” within an NSString?

You can use NSRegularExpression class with a pattern like #\w+ (\w stands for word characters).

NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"#(\\w+)" options:0 error:&error];
NSArray *matches = [regex matchesInString:string options:0 range:NSMakeRange(0, string.length)];
for (NSTextCheckingResult *match in matches) {
    NSRange wordRange = [match rangeAtIndex:1];
    NSString* word = [string substringWithRange:wordRange];
    NSLog(@"Found tag %@", word);
}

How to only view tweets that have a specific hashtag

Is there a way to run a query for hashtags in STTwitter?

Yes! Use the following method on STTwitterAPI:

[_twitter postStatusesFilterKeyword:@"#Apple"
                         tweetBlock:^(NSDictionary *tweet) {
                           //
                       } errorBlock:^(NSError *error) {
                           //
                       }];

Also, the OS X demo project provides a GUI to test that:

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