Question

I am trying to write a method:

- (NSDictionary *)wordFrequencyFromString:(NSString *)string {}

where the dictionary returned will have the words and how often they were used in the string provided. Unfortunately, I can’t seem to find a way to iterate through words in a string to analyze each one – only each character which seems like a bit more work than necessary. Any suggestions?

Answer 1

NSString has -enumerateSubstringsInRange: method which allows to enumerate all words directly, letting standard api to do all necessary stuff to define word boundaries etc:

[s enumerateSubstringsInRange:NSMakeRange(0, [s length])
                      options:NSStringEnumerationByWords
                   usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
                       NSLog(@"%@", substring);
                   }];

In the enumeration block you can use either NSDictionary with words as keys and NSNumber as their counts, or use NSCountedSet that provides required functionality for counts.