Retrieve 1 specific key from several NSArrays and add them together - ios

Question

In my app, I am needing to loop through each NSArray, get the NSInteger associated with the key 'people' in the NSArray, and then add them all together. What would be a good starting point for first retrieving each specific NSInteger from each NSArray?
The array in question returns like this in console.
(
"<Prayers:DDomBXIONY:(null)> {\n Anonymous = 1;\n DeviceID = 123;\n FirstName = Name;\n LastName = Name;\n Location = HI;\n PrayerWarriors = 8;\n Request = Hi;\n Title = Hi;\n UserId = RtXN6QZsgaIiPw4SjFWGtkxXx;\n dateMade = \"Jan_09_2015\";\n}"
)
Basically just need to retrieve NSInteger from each PrayerWarriors key, and add them all together.
(
"<Prayers:DDomBXIONY:(null)> {\n Anonymous = 1;\n DeviceID = 123;\n FirstName = Name;\n LastName = Name;\n Location = HI;\n PrayerWarriors = 8;\n Request = Hi;\n Title = Hi;\n UserId = RtXN6QZsgaIiPw4SjFWGtkxXx;\n dateMade = \"Jan_09_2015\";\n}",
"<Prayers:yG7GC4bCIH:(null)> {\n Anonymous = 1;\n DeviceID = 123;\n FirstName = Name;\n LastName = Name;\n Location = bye;\n PrayerWarriors = 0;\n Request = bye;\n Title = bye;\n UserId = RtXN6QZsgaIiPw4SjFWGtkxXx;\n dateMade = \"Jan_09_2015\";\n}"
)

Answer 1

So without understanding exactly how your PFObject works, I'm going to assume it's like a dictionary.
Add each of your objects to a single array:
NSMutableArray *arrayHoldingPrayersObjects = [NSMutableArray alloc] init];
arrayHoldingPrayersObjects[0] = prayerObject1;
arrayHoldingPrayersObjects[1] = prayerObject2;
arrayHoldingPrayersObjects[2] = prayerObject3;
etc...
Then create a integer variable outside of a for loop and iterate through your objects, adding the value for PrayerWarrior at each iteration.
int totalPrayerWarriors = 0;
for (int i = 0; i < arrayHoldingPrayersObjects.count; i++)
{
NSMutableDictionary *prayerObject = arrayHoldingPrayersObjects[i];
totalPrayerWarriors += [prayerObject objectForKey:#"PrayerWarriors"] intValue];
}
You should end up with a correct total from all arrays. Do some tests to make sure it's accurate for you. Hope this helps.
*EDIT
The error you're getting indicates that it actually is a NSMutableArray, which you can't access using methods like objectForKey, so... there must be a method provided by PFObject that allows you to do that. OR, if PrayerWarriors is reliably the [5]th value (including 0) in the array, then you might be able to access it by index.
replace the lines:
NSMutableDictionary *prayerObject = arrayHoldingPrayersObjects[i];
totalPrayerWarriors += [prayerObject objectForKey:#"PrayerWarriors"] intValue];
with
NSMutableArray *prayerObject = arrayHoldingPrayersObjects[i];
totalPrayerWarriors += prayerObject[5];

Answer 2

Not sure where the mutable array is coming from. Parse.com will always produce immutable arrays as far as I know. So lets say you've retrieved Prayers with:
PFQuery *query = [PFQuery queryWithClassName:#"Prayers"];
[query findObjectsInBackgroundWithBlock:^(NSArray *prayers, NSError *error) {
// see how it's an NSArray, not mutable
}];
Now you want the total of the retrieved PrayerWarrior attributes, so...
[query findObjectsInBackgroundWithBlock:^(NSArray *prayers, NSError *error) {
NSInteger total = 0;
for (PFObject *p in prayers) {
NSNumber *warriorCount = p[#"PrayerWarriors"];
total += [warriorCount intValue]; // notice we cannot add nsnumbers directly (we need intValue)
}
NSLog(#"total warriors = %d", total);
}];