count occurrences in a NSArray - ios

Question

this is a part of my code from a NSArray:
2012-06-03 16:03:45.140 test[4178:f803] data (
{
receiver = david;
sender = james;
idMessage = 248;
},
{
receiver = david;
sender = james;
idMessage = 247;
},
{
receiver = david;
sender = Marc;
idMessage = 246;
}
)
I want the number of messages sent by sender to receiver or something like that
james = 2;
marc = 1;

Answer 1

"data" is the NSArray, which appears to contain NSDictionary objects.
So you'd want to loop through the array this way:
NSNumber * countOfSender;
NSString * nameOfSender;
NSMutableDictionary * countDictionary = [[NSMutableDictionary alloc] initWithCapacity: 1];
// go through the original array to examine each sender
for(NSDictionary *anEntry in data)
{
nameOfSender = [anEntry objectForKey: #"sender"];
if(sender)
{
countOfSender = [countDictionary objectForKey: nameOfSender];
if(countOfSender == NULL)
{
// create a new count entry for this particular sender
countOfSender = [NSNumber numberWithInt: 1];
} else {
// increment the previous count
countOfSender = [NSNumber numberWithInt: [countOfSender intValue] + 1];
}
[countDictionary setObject: countOfSender forKey: nameOfSender];
}
}
// now print out the outputs
for(nameOfSender in [countDictionary allKeys])
{
countOfSender = [countDictionary objectForKey: nameOfSender];
NSLog( #"%# : %d" nameOfSender, [countOfSender intValue] );
}

Answer 2

You would do something like..
NSMutableArray *array = [NSMutableArray array];
for(id object in yourArray) {
NSLog("sender:%# id:%i",[object valueForKey:#"sender"],[[object valueForKey:#"idMessage"] intValue]);
NSMutableDictionary *dict = [
NSMutableDictionary dictionary];
[dict setValue:[object valueForKey:#"sender"] forKey:#"sender"];
[dict setValue:[NSNumber numberWithInt:[[object valueForKey:#"idMessage"] intValue]] forKey:#"idMessage"];
[array addObject:dict];
}
NSLog(#"%#",array);