Filtering NSArray/NSDictionary using NSPredicate - iphone

Question

I've been trying to filter this array (which is full of NSDictionaries) using NSPredicate...
I have a very small amount of code that just isn't working...
The following code should change label.text to AmyBurnett34, but it doesn't...
NSPredicate *pred = [NSPredicate predicateWithFormat:#"id = %#", [[mightyPlistDict objectForKey:#"pushesArr"] objectAtIndex:indexPath.row]];
NSLog(#"%#",pred);
label.text = [[[twitterInfo filteredArrayUsingPredicate:pred] lastObject] objectForKey:#"screen_name"];
NSLog(#"%#",twitterInfo);
And here is what gets NSLoged...
2012-08-05 11:39:45.929 VideoPush[1711:707] id == "101323790"
2012-08-05 11:39:45.931 VideoPush[1711:707] (
{
id = 101323790;
"screen_name" = AmyBurnett34;
},
{
id = 25073877;
"screen_name" = realDonaldTrump;
},
{
id = 159462573;
"screen_name" = ecomagination;
},
{
id = 285234969;
"screen_name" = "UCB_Properties";
},
{
id = 14315150;
"screen_name" = MichaelHyatt;
}
)
Just for the heads up if you also NSLog this... the array is empty...
NSLog(%#,[twitterInfo filteredArrayUsingPredicate:pred]);

Answer 1

The problem is that your predicate is using comparing with a string and your content is using a number. Try this:
NSNumber *idNumber = [NSNumber numberWithLongLong:[[[mightyPlistDict objectForKey:#"pushesArr"] objectAtIndex:indexPath.row] longLongValue]];
NSPredicate *pred = [NSPredicate predicateWithFormat:#"id = %#", idNumber];

Answer 2

You don't know for sure that the value of "id" is a string - it might be a NSNumber. I suggest:
NSUInteger matchIdx = ...;
NSUInteger idx = [array indexOfObjectPassingTest:^BOOL(NSDictionary *dict, NSUInteger idx, BOOL *stop)
{
id obj = [dict objectForKey:#"id"];
// NSLog the class if curious using NSStringFromClass[obj class];
NSUInteger testIdx = [obj integerValue]; // works on strings and numbers
return testIdx == matchIdx;
}
if(idx == NSNotFound) // handle error
NSString *screenName = [[array objectAtIndex:idx] objectForKey:#"screen_name"];

Answer 3

NSPredicate is used for filtering arrays, not sorting them.
To sort an array, use the sortedArrayUsingDescriptors method of NSArray.
An an example:
// Define a sort descriptor based on last name.
NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:#"lastName" ascending:YES];
// Sort our array with the descriptor.
NSArray *sortedArray = [originalArray sortedArrayUsingDescriptors:[NSArray arrayWithObjects:descriptor, nil]];