Q:

how to verify if an element exsit or not in an NSMutubleArray

I'm new to objective-c.
I have an NSMutableArray . I wrote this:
for (int i=0; i<[allCombinations count]; i++)
{
    NSString *date = [[allCombinations objectAtIndex:i] objectForKey:@"keydate"];
    NSString *cachdepeDate = [date substringToIndex:8];
}

How can i see if cachdepeDate is alrady exsit in my NSMutbleArray?
If it is not exist how do I add it? 
Should I make for loop, or there is a method for this? 
Can i sort the NSMutbleArray? 
Dates are in this format: "20110531" "YYYYMMDD". 
Thank you!

A:

Use the following
[yourArray containsObject:cachdepeDate];

