how to avoid the c-style for loop ?

import Foundation

let string = "e5cfb500"

for var index = string.startIndex; index < string.endIndex; index = index.advancedBy(2) {
    let rangeOfCharacterPair = Range<String.Index>(index..<index.advancedBy(2))
    let characterPair = string.substringWithRange(rangeOfCharacterPair)
    
    print(characterPair)
}

What about this? Ranges and maps are GREAT :). Also, this uses Swift's String subscript instead of substringWithRange dropping the need for Foundation.

let string = "e5cfb500"

let pairsCount = string.characters.count / 2
let pairs = (0..<pairsCount).map { pairNumber -> String in
    let pairStartPosition = string.startIndex.advancedBy(pairNumber * 2)
    return string[pairStartPosition...pairStartPosition.advancedBy(1)]
}

for pair in pairs {
    print(pair)
}

Wait a second, I didn't see @paoloboschini's comment using stride. That's clever! How about this even?

let string = "e5cfb500"

let pairs = 0.stride(to: string.characters.count, by: 2).map { pairStartPosition -> String in
    return string[string.startIndex.advancedBy(pairStartPosition)...string.startIndex.advancedBy(pairStartPosition + 1)]
}

for pair in pairs {
    print(pair)
}