Dropping first and last

One way to remove both the first and last letters of a string can be done by nesting the NSString methods substringToIndex: and substringFromIndex::

NSString *helloString = @"Hello";

NSString *butFirstAndLast = [[helloString substringToIndex:helloString.length - 1] substringFromIndex:1];
NSLog(@"%@", butFirstAndLast); // "ell"

Or we can do this by by making an NSRange of everything but the first and last letters, and using the NSString substringWithRange: method:

NSString *helloString = @"Hello";

NSRange endsRange = NSMakeRange(1, helloString.length - 2);
NSString *butFirstAndLast = [helloString substringWithRange:endsRange];
NSLog(@"%@", butFirstAndLast); // "ell"

In Swift, if we have a mutable String, we can remove the first and last letters with removeAtIndex:

var helloString = "Hello"

let start = helloString.startIndex
helloString.removeAtIndex(start)
println(helloString) // "ello"

let end = helloString.endIndex.predecessor()
helloString.removeAtIndex(end)
println(helloString) // "ell"

Or we can use String subscripting, using a Range with the startIndex.successor() and endIndex.predecessor():

var helloString = "Hello"

let endsRange = Range(start: helloString.startIndex.successor(),
                        end: helloString.endIndex.predecessor())

let butFirstAndLast = helloString[endsRange]
println(butFirstAndLast) // "ell"

The Swift standard library also has the dropFirst and dropLast functions. These take a type that conforms to the Sliceable protocol and return a new slice that contains everything but the first or last element.

So this could be used to drop the first and/or last elements of an Array:

let arrayOfInts = [0, 1, 2, 3, 4, 5, 6]

let butFirst = dropFirst(arrayOfInts)
println(butFirst) // "[1, 2, 3, 4, 5, 6]"

let butLast = dropLast(arrayOfInts)
println(butLast) // "[0, 1, 2, 3, 4, 5]"

// Nest the functions together to drop both elements.
let butFirstAndLast = dropFirst(dropLast(arrayOfInts))
println(butFirstAndLast) // "[1, 2, 3, 4, 5]"

And to drop the first and/or last letters of a String:

let helloString = "Hello"

let butFirst = dropFirst(helloString)
println(butFirst) // "ello"

let butLast = dropLast(helloString)
println(butLast) // "Hell"

// Nest the functions together to drop both letters.
let butFirstAndLast = dropFirst(dropLast(helloString))
println(butFirstAndLast) // "ell"