Question

I need to append strings to an array kept inside of a dictionary each time a word matches a pattern of another word. The second line below (setObject) overwrites instead of appending.
The end result should be arrays in a dictionary where the the key(pattern) identifies many strings that fit that pattern.

    NSMutableDictionary *eqClasses = [[NSMutableDictionary alloc] init];
    [eqClasses setObject:tempWordStr forKey:wordPattern];

Is there an easy way to append?

Answer 1

Try this:

NSMutableArray* array = [eqClasses objectForKey:wordPattern];
if(!array) {
  // create new array and add to dictionary if wordPattern not found
  array = [NSMutableArray array];
  [eqClasses setObject:array forKey:wordPattern];
}
[array addObject:tempWordStr];