Returning the number of objectForKey - iphone

Question

I have a part of my code that returns the numberOfRowsInSection.
Code
for (NSDictionary *consoleDictionary in [self arrayFromJSON]) {
if ([[consoleDictionary objectForKey:#"model"] isEqualToString:#"PlayStation 3"]) {
NSLog(#"%#", consoleDictionary);
}
}
Output
2013-02-03 22:37:08.468 PageControl01[5782:c07] {
console = PlayStation;
game = "007 Legends";
id = 1;
model = "PlayStation 3";
publisher = "Electronic Arts";
}
2013-02-03 22:37:08.478 PageControl01[5782:c07] {
console = PlayStation;
game = "Ace Combat: Assault Horizon";
id = 2;
model = "PlayStation 3";
publisher = Namco;
}
This one is apparently right because it logs all the "PlayStation 3" model. However, this is not what I need. I want to log the number of "PlayStation 3"'s. So I tweak the code a little bit and then this:
for (NSDictionary *consoleDictionary in [self arrayFromJSON]) {
if ([[consoleDictionary objectForKey:#"model"] isEqualToString:#"PlayStation 3"]) {
NSLog(#"%d", [consoleDictionary count]);
}
}
Output
2013-02-03 22:39:43.605 PageControl01[5816:c07] 5
2013-02-03 22:39:43.605 PageControl01[5816:c07] 5
This one is pretty near yet so close. Instead of logging the number 5, it should log the number 2 since there are only 2 "PlayStation 3".
Please help.

Answer 1

You don't need to explicitly loop through the array.
NSIndexSet *is = [array indexesOfObjectsPassingTest:^(id obj, NSUInteger idx, BOOL *stop) {
return [[obj objectForKey:#"model"] isEqualToString:#"PlayStation 3"];
}];
int numOfPS3s = is.count;

Answer 2

It is logging the number 5 because there is 5 keys in each of your dictionaries (console, game, id, model, publisher). If instead of logging the [consoleDictionary count] you simply add one to an int counter each time, you would get the expected result in your counter at the end.
You can obtain the number of objects is a much more easier way: [self arrayFromJSON] is an array
Typically:
NSInteger nbPS3 = [[self arrayFromJSON] indexesOfObjectsPassingTest:^(id obj, NSUInteger idx, BOOL *stop) {
return [obj[#"model"] isEqualToString:#"PlayStation 3"];
}].count

Answer 3

Yes, count is always the total count, not the index, not the count of matches. Using indexesOfObjectsPassingTest is the most direct solution for this specific question, but if you're interested in other techniques for iterating through your result set, but also keeping track of not only the object, but also the index, consider these two approaches, too:
for (NSInteger i = 0; i < [self.arrayFromJSON count]; i++) {
if ([[[self.arrayFromJSON objectAtIndex:i] objectForKey:#"model"] isEqualToString:#"PlayStation 3"]) {
NSLog(#"%d", i);
}
}
or
[self.arrayFromJSON enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([[obj objectForKey:#"model"] isEqualToString:#"PlayStation 3"]) {
NSLog(#"%d", idx);
}
}];
Obviously, if you're looking for how many records match, you'd just increment your own counter, rather than logging the index for each match.