Convert spelled out number to number

Question

Is there a way, in Objective-C/Cocoa, to convert spelled out words to an NSNumber or equivalent in multiple languages?

For example:

convert three to 3 or convert ocho to 8 (Spanish).

Also slightly different, but 3 1/2 to 3.5

I could write my own code to do this, but I was hoping there was a built-in way to do this. Getting the translations of every number in several languages is something I'd like to avoid.

Answer 1

NSNumberFormatter can convert from text to numbers:

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
formatter.numberStyle = NSNumberFormatterSpellOutStyle;

NSLog(@"%@", [formatter numberFromString:@"thirty-four"]);
NSLog(@"%@", [formatter numberFromString:@"three point five"]);

formatter.locale = [[NSLocale alloc]initWithLocaleIdentifier:[NSLocale localeIdentifierFromComponents:@{NSLocaleLanguageCode: @"es"}]];

NSLog(@"%@", [formatter numberFromString:@"ocho"]);

There are serious limitations as to what it can handle (it doesn't auto detect languages, if you deviate from the expected format (e.g. "thirty four" instead of "thirty-four"), fractions, etc.), but for the narrow domain, it appears to do the job.

Answer 2

NSLinguisticTagger will flag numbers for you in multiple languages.

NSArray * texts = @[@"It's 3 degrees outside", @"Ocho tacos", @"What is 3 1/2?", @"ocho"];
for (NSString * text in texts)
{
    NSLinguisticTaggerOptions options = NSLinguisticTaggerOmitWhitespace | NSLinguisticTaggerJoinNames;
    NSArray * tagSchemes = [NSLinguisticTagger availableTagSchemesForLanguage:@"en"];
    tagSchemes = [tagSchemes arrayByAddingObjectsFromArray:[NSLinguisticTagger availableTagSchemesForLanguage:@"es"]];

    NSLinguisticTagger * tagger = [[NSLinguisticTagger alloc] initWithTagSchemes:tagSchemes
                                                                                 options:options];
    [tagger setString:text];

    [tagger enumerateTagsInRange:NSMakeRange(0, [text length])
                          scheme:NSLinguisticTagSchemeNameTypeOrLexicalClass
                         options:options
                      usingBlock:^(NSString *tag, NSRange tokenRange, NSRange sentenceRange, BOOL *stop)
        {
            NSString *token = [text substringWithRange:tokenRange];
            NSLog(@"%@: %@", token, tag);
        }];
}

This does leave you with the task of identifying how and when to do things like fraction resolution.