Sort in Objective-C

In Objective-C, arrays can be sorted using the sortedArrayUsingComparator method provided by the NSArray class. This method takes a comparator block as an argument, which defines the ordering of the array elements.

Here's an example of sorting an array of integers in ascending order:

NSArray *numbers = @[@5, @2, @7, @1, @8];
NSArray *sortedNumbers = [numbers sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    return [obj1 compare:obj2];
}];
NSLog(@"%@", sortedNumbers);  // Output: [1, 2, 5, 7, 8]

In this example, the sortedArrayUsingComparator method is called on the numbers array and passed a comparator block. The block takes two arguments obj1 and obj2 of type id, representing the elements being compared. The block returns an NSComparisonResult, indicating whether obj1 is less than, equal to, or greater than obj2.

The compare: method is used to compare the two elements obj1 and obj2. This method is implemented by the NSNumber class (since the elements in our array are NSNumber objects) and returns an NSComparisonResult based on the values of the numbers.

To sort the array in descending order, you can reverse the order of the comparison result in the comparator block:

NSArray *numbers = @[@5, @2, @7, @1, @8];
NSArray *sortedNumbers = [numbers sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    return [obj2 compare:obj1];
}];
NSLog(@"%@", sortedNumbers);  // Output: [8, 7, 5, 2, 1]

This will sort the numbers in the array in descending order.