iPhone how to get a running tally of unique items in an Array?

Lets say I have an NSArray full of animal objects and their names are string attributes. As I iterate through the array, how would I get a running tally of similar names?

Cat - Bob count:1

开发者_开发问答

Dog - Sally count:1

Cat - Bob count:2

Bunny - Bob count:3

Fish - Sally count:2

How would I get these ints if the names are dynamic, not static?

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The most straightforward way would be to use an NSMutableDictionary. For each name, try to fetch the NSNumber for that name from the dictionary. If one was found, add 1 and store it back; if not, create a new one with the value 1 and store it.

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I guess you could use a NSMutableDictionary in order to hold a count of the names.

Something like:

NSMutableDictionary *dic = [[NSMutableDictionary alloc] initWithCapacity:10];

NSString *name = [NSString stringWithFormat:@"Bob"];    
NSNumber *number = (NSNumber *)[dic objectForKey:name];

if (number == nil) // There is no occurrence of the name in Dictionary
{
    number = [NSNumber numberWithInt:1];
    [dic setObject:number forKey:name];
}
else // There is already an occurrence of the name in dictionary, so increment counter
{
    number = [NSNumber numberWithInt:(number.intValue + 1)]; // Increments counter for Name
    [dic objectForKey:name];
}

The line "NSNumber *number = (NSNumber *)[dic objectForKey:name]" retrieves the number of times a specific name appeared.

You can also use [dic allKeys]; to retrieve all the names in that dictionary.