iOS: How to find insertion position in sorted NSMutableArray

Question

I have an NSMutableArray of sorted objects, which are displayed in a UITableView.

I want to insert a new object into the array and update the table view - which requires the index of the newly inserted object.

I can't find any system message to tell me the correct insertion index into the array which I need to update the table view.

The best I can find is:

• add new object
• sort
• using old copy of array, find the location of the new object (which requires searching)

or

• write my own search for insertion position

Surely, there must be a message to find the insertion position in a sorted array? Or am I missing something obvious here?

Answer 1

You can use indexOfObject:inSortedRange:options:usingComparator: method on the entire array. This method performs a binary search on a range that you pass, and gives you the insertion point when you use the NSBinarySearchingInsertionIndex option:

NSUInteger insPoint = [myArray
    indexOfObject:toInsert
    inSortedRange:NSMakeRange(0, [myArray count])
    options:NSBinarySearchingInsertionIndex
    usingComparator:^(id lhs, id rhs) {
        return // return the result of comparing two objects
    }
];