[swift3] String search

String.find.swift

extension String {
    func first(_ search: String) -> Int {
        var hit: Int = -1
        next: for i in 0..<(self.characters.count - search.characters.count) {
            for j in 0..<search.characters.count {
                let n = self.characters[self.index(self.startIndex, offsetBy: (i+j))]
                let s = search.characters[search.index(search.startIndex, offsetBy: j)]
                if n != s {
                    break
                } else if j == search.characters.count - 1 {
                    hit = i
                    break next
                }
            }
        }

        return hit
    }
}


let r = "🐮🐒🐶🐾🐑🐮🐷🐴".first("🐾")
print("r = \(r)")