NSMutableArray add object with order

You can use -[NSArray indexOfObject:inSortedRange:options:usingComparator:] to ask an NSArray for the index where an object should be inserted given an array range that’s currently sorted.

For example, assuming the entire array is sorted::

NSMutableArray *array = …;id newObject = …;NSComparator comparator = …;NSUInteger newIndex = [array indexOfObject:newObject                             inSortedRange:(NSRange){0, [array count]}                                   options:NSBinarySearchingInsertionIndex                           usingComparator:comparator];[array insertObject:newObject atIndex:newIndex];

Since this method uses binary search, it is more efficient than iterating over all elements in the array.

The comparator is a block object that receives two objects of type id and returns an NSComparisonResult value.

To inject element to known index (position) use

- (void)insertObject:(id)anObject atIndex:(NSUInteger)index

http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSMutableArray_Class/Reference/Reference.html

And to find position of object previously placed into NSMutableArray use

- (int)indexOfObject:(id)anObject

NSMutableArray - Get Arrays Index Integer By Searching With A String

Section Finding Objects in an Array
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/NSArray.html

I'd just add the new object at either end and sort the array again. If the array you're adding to is already sorted, the re-sort that moves one object is going to be about as quick as anything you'd implement yourself.

NSMutableArray *things; // populated id newObject;...[things addObject:newObject atIndex:0];[things sortUsingSelector:@selector(compare:)];