More Functional / Swift way to convert time to minutes - swift

Question

I'm trying to convert a length of time in "Hours:Minutes" to "minutes". Time is given as a String, and I want to return a Double of minutes.
Currently I'm using the following function:
func convertMinHoursToDouble(length: String) -> Double {
var hours = 0.0
var minutes = 0.0
let lengthCleaned = length.stringByReplacingOccurrencesOfString(":", withString: "")
var count = 0
for char in lengthCleaned.characters {
if count == 0 {
hours = Double("\(char)")! * 60
} else if count == 1 {
minutes = Double("\(char)")! * 10
} else if count == 2 {
minutes = Double("\(char)")! + minutes
}
++count
}
return hours+minutes
}
let time = "2:16"
let convertedTime = convertMinHoursToDouble(time)
print(convertedTime) // prints 136.0
This works, however I'm trying to do this in a more functional / Swift way. How can it be done with the reduce function. This is the closest I can get to the solution.
let convertedTime = time.characters.reduce(0) { (dub, char) in dub + Double(String(char))! }

Answer 1

The pure Swift way would be :
let time = "02:16"
let converted = time.characters.split(":")
.flatMap { Int(String($0)) }
.reduce(0) { $0 * 60 + $1 }
print(converted) //"136\n"

Answer 2

Functional solution:
func convertMinHoursToDouble(time: String) -> Int {
let timeComps = (time as NSString).componentsSeparatedByString(":") as [NSString]
return timeComps.reduce(0) { acc, item in
acc * 60 + item.integerValue
}
}
let time = "02:15"
let convertedTime = convertMinHoursToDouble(time)
print(convertedTime)
You split the string into components, and reduce on that array. This works like a charm also for strings like "03:24:34" for which it computes the time in seconds.
You can add additional validation logic if you want to deal with malformed strings: no ":", more than one ":", invalid minutes value (e.g. 78), etc.