Here is a code who worked perfectly in Swift 1.1

At the beginning of my class I have

```
var bytes = [UInt8]?()

```

later I have

```
func hexString() -> String? {
    if let b = bytes {
        return b.map({NSString(format: "%02x", $0)}).reduce("", +)
    }
    return nil
}

```

Swift 1.2 gives me

*Missing argument label 'combine:' in call*

and thus wants me to rephrase my map reduce this way

```
return b.map({NSString(format: "%02x", $0)}).reduce("", combine: +)

```

note the explicit **combine** for the second `reduce` argument. if I do that though I get another error on the `+`:

*Could not find an overload for '+' that accepts the supplied arguments*

This error makes no sense to me since what `NSString(format:)` produces is a NSString, so it should work with `+`, right?