Cfrgtkky

I'd building an app that uses hashtags, like Twitter or Tweetbot. When you're typing a message, if you type the hashtag symbol, I'd like to suggest tags that match the current one you're typing.

I've already figured out how to get the UITableView to appear and show a list of hashtags, but what I can't figure out is how to do the following:

1. Get the NSRange of the current word being typed,


2. See if that range is formatted like a hashtag (NSRegularExpression @"#\w\w*")


3. (From here on out, I've got the code figured out to search for matching hashtags and show them in the UITableView)

Can anyone help me with steps 1 and 2? I've been thinking about using textViewDidChange:, but I'm concerned that the app's performance might suffer if I'm constantly running methods every time the characters change.

Thanks!

I figured it out! I wound up using the textViewDidChange: and textViewDidChangeSelection: methods.

To get the NSRange of the current hashtag being typed, I ran a for loop over the NSRegularExpression matches in the text string. From there, I used NSLocationInRange to find out if the current cursor position intersected any of the hashtags.

Here's the code:

//Get the ranges of current hashtags

NSArray *hashtagRanges = [StringChecker rangesOfHashtagsInString:textView.text];

NSTextCheckingResult *currentHashtag;



if ([hashtagRanges count] >0)

{

    //List the ranges of all the hashtags

    for (int i = 0; i<[hashtagRanges count]; i++) 

    {

        NSTextCheckingResult *hashtag = [hashtagRanges objectAtIndex:i];

        //Check if the currentRange intersects the hashtag

        //Have to add an extra space to the range for if you're at the end of a hashtag. (since NSLocationInRange uses a < instead of <=)

        NSRange currentlyTypingHashtagRange = NSMakeRange(hashtag.range.location, hashtag.range.length + 1);

        if (NSLocationInRange(currentRange.location, currentlyTypingHashtagRange))

        {

            //If the cursor is over the hashtag, then snag that hashtag for matching purposes.

            currentHashtag = hashtag;

        }

    }



    if (currentHashtag){

        //If we found one hashtag that we're currently editing



        //Display the hashtag suggester, feed it the current hashtag for matching.

        [self showTagTable];



        //Get the current list of hashtags into an array

        NSFetchRequest *hashtagRequest = [[NSFetchRequest alloc] init];

        NSEntityDescription *tagEntityDescription = [NSEntityDescription entityForName:@"Tags" 

                                                                inManagedObjectContext:self.note.managedObjectContext];

        [hashtagRequest setEntity:tagEntityDescription];

        NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"dateLastUsed" 

                                                                         ascending:YES];

        NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];

        [hashtagRequest setSortDescriptors:sortDescriptors];



        NSPredicate *tagPredicate = [NSPredicate predicateWithFormat:@"name contains[c] %@", [noteTextView.text substringWithRange:currentHashtag.range]];

        [hashtagRequest setPredicate:tagPredicate];



        tagsToDisplay = (NSMutableArray *)[self.note.managedObjectContext executeFetchRequest:hashtagRequest error:nil];

        [tagListTable reloadData];



        //If there are no matching hashtags, then let's hide the tag table.

        if ([tagsToDisplay count] == 0) 

        {

            [self hideTagTable];

            return;

        }



    }

The StringChecker class is a custom one that I wrote, it just has class methods that parse the strings. I made StringChecker a class because the methods are used in several places in the app. Here's the method:

    #pragma mark - Hashtag Methods

+(NSArray *)rangesOfHashtagsInString:(NSString *)string {

    NSRegularExpression *hashtagDetector = [[NSRegularExpression alloc] initWithPattern:@"#\w\w*" 

                                                                                options:NSRegularExpressionCaseInsensitive 

                                                                                  error:nil];    

    NSArray *hashtagRanges = [hashtagDetector matchesInString:string

                                                      options:NSMatchingWithoutAnchoringBounds

                                                        range:NSMakeRange(0, string.length)];

    return hashtagRanges;

}



+(NSUInteger)numberOfHashtagsInString:(NSString *)string {

    NSRegularExpression *hashtagDetector = [[NSRegularExpression alloc] initWithPattern:@"#\w\w*" 

                                                                                options:NSRegularExpressionCaseInsensitive 

                                                                                  error:nil];

    NSUInteger numberOfHashtags = [hashtagDetector numberOfMatchesInString:string

                                                                   options:NSRegularExpressionCaseInsensitive

                                                                     range:NSMakeRange(0, string.length)];

    return numberOfHashtags;

}

Another way I figured out to do this is as follows.

In the - (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text function I put a listener for a # being typed which begins recording the characters following the hash until the user types a space at which time it resets.

if ([text isEqualToString:@"#"]) {

    recordingHashTag = YES;

    startParse = range.location;



}else if ([text isEqualToString:@" "]) {

    currentHashTag = nil;

    recordingHashTag = NO;

    theTable.hidden = YES;



}



if (recordingHashTag == YES) {

    NSString *value;

    if (startParse > [textView.text length] - startParse) {

        value = [textView.text substringWithRange:NSMakeRange(startParse, [textView.text length] - startParse)];

        [self filterHashTagTableWithHash:value];

    }

}

If the BOOL recordingHashTag is set to YES I pass the substring containing the hashtag text to a function which searches a pre populated array of hashtags. If there is a match it adds that entry to a filtered array of hashtags which it uses to populate the tableview on the fly.

-(void)filterHashTagTableWithHash:(NSString *)hash{



    [self.filterHashTagArray removeAllObjects];



    for (NSString *hashTag in self.hashTagArray ){

        NSRange result = [hashTag rangeOfString:hash options:NSCaseInsensitiveSearch];

        if (result.location != NSNotFound) {

            [filterHashTagArray addObject:hashTag];

        }

    }

    if (filterHashTagArray.count) {

        theTable.hidden = NO;

    }else{

        theTable.hidden = YES;

    }



    [self.theTable reloadData];

}

The final step is to insert the hash tag when the user clicks on the entry in the table.

    - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{

    UITableViewCell *cell = (UITableViewCell*)[self tableView:theTable cellForRowAtIndexPath:indexPath];



    NSString *newString = [textViewComment.text stringByReplacingCharactersInRange:NSMakeRange(startParse, [textViewComment.text length] - startParse) withString:cell.textLabel.text];

    textViewComment.text = newString;

}

Just don't forget to clear out your variables when a user backspaces mid hash tag.