Capitalize first letter of every sentence in NSString

Question

How can I capitalize the first letter of each sentence in an NSString? For example, the string: @"this is sentence 1. this is sentence 2! is this sentence 3? last sentence here." should become: @"This is sentence 1. This is sentence 2! Is this sentence 3? Last sentence here."

Answer 1

static NSString *CapitalizeSentences(NSString *stringToProcess) {
    NSMutableString *processedString = [stringToProcess mutableCopy];


    NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en"];


    // Ironically, the tokenizer will only tokenize sentences if the first letter
    // of the sentence is capitalized...
    stringToProcess = [stringToProcess uppercaseStringWithLocale:locale];


    CFStringTokenizerRef stringTokenizer = CFStringTokenizerCreate(kCFAllocatorDefault, (__bridge CFStringRef)(stringToProcess), CFRangeMake(0, [stringToProcess length]), kCFStringTokenizerUnitSentence, (__bridge CFLocaleRef)(locale));


    while (CFStringTokenizerAdvanceToNextToken(stringTokenizer) != kCFStringTokenizerTokenNone) {
        CFRange sentenceRange = CFStringTokenizerGetCurrentTokenRange(stringTokenizer);

        if (sentenceRange.location != kCFNotFound && sentenceRange.length > 0) {
            NSRange firstLetterRange = NSMakeRange(sentenceRange.location, 1);

            NSString *uppercaseFirstLetter = [[processedString substringWithRange:firstLetterRange] uppercaseStringWithLocale:locale];

            [processedString replaceCharactersInRange:firstLetterRange withString:uppercaseFirstLetter];
        }
    }


    CFRelease(stringTokenizer);


    return processedString;
}

Answer 2

Use

-(NSArray *)componentsSeparatedByCharactersInSet:(NSCharacterSet *)separator

put all the separator(? ,. ,! ) from which you expect beginning of new sentence, make sure to put back the actual separator and capitalize the first object in the array and then use

-(NSString *)componentsJoinedByString:(NSString *)separator

to join them back with space separator

for capitalizing the first letter of each sentence run for loop for all elements of the array.

NSString *txt = @"hello!" txt = [txt stringByReplacingCharactersInRange:NSMakeRange(0,1) withString:[[txt substringToIndex:1] uppercaseString]];

Answer 3

This seems to work:

NSString *s1 = @"this is sentence 1. this is sentence 2! is this sentence 3? last sentence here.";

NSMutableString *s2 = [s1 mutableCopy];
NSString *pattern = @"(^|\\.|\\?|\\!)\\s*(\\p{Letter})";
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern options:0 error:NULL];
[regex enumerateMatchesInString:s1 options:0 range:NSMakeRange(0, [s1 length]) usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
    //NSLog(@"%@", result);
    NSRange r = [result rangeAtIndex:2];
    [s2 replaceCharactersInRange:r withString:[[s1 substringWithRange:r] uppercaseString]];
}];
NSLog(@"%@", s2);
// This is sentence 1. This is sentence 2! Is this sentence 3? Last sentence here.

• "(^|\\.|\\?|\\!)" matches the start of the string or ".", "?", or "!",
• "\\s*" matches optional white space,
• "(\\p{Letter})" matches a letter character.

So this pattern finds the first letter of each sentence. enumerateMatchesInString enumerates all the matches and replaces the occurrence of the letter by the upper case letter.