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Parse user friendly time duration string in Swift
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| extension DateComponents { | |
| subscript(unit: String) -> Int { | |
| get { | |
| switch unit { | |
| case "month": | |
| return self.month! | |
| case "day": | |
| return self.day! | |
| case "hour": | |
| return self.hour! | |
| case "minute": | |
| return self.minute! | |
| case "second": | |
| return self.second! | |
| default: | |
| fatalError("unknown unit \(unit)") | |
| } | |
| } | |
| set(newValue) { | |
| switch unit { | |
| case "month": | |
| self.month = newValue | |
| case "day": | |
| self.day = newValue | |
| case "hour": | |
| self.hour = newValue | |
| case "minute": | |
| self.minute = newValue | |
| case "second": | |
| self.second = newValue | |
| default: | |
| fatalError("unknown unit \(unit)") | |
| } | |
| } | |
| } | |
| } | |
| func timeInterval(parsing input: String) -> TimeInterval { | |
| let components = dateComponentFromNaturalLanguageString(input) | |
| let reference = Date(timeIntervalSinceReferenceDate: 0) | |
| let date = Calendar(identifier: .gregorian).date(byAdding: components, to: reference) | |
| return date!.timeIntervalSinceReferenceDate | |
| } | |
| func dateComponentFromNaturalLanguageString(_ input: String) -> DateComponents { | |
| // Define the time units we can understand | |
| let timeUnits = [ | |
| // Unit kind => [Unit aliases...] | |
| "month": ["months", "month", "mon"], | |
| "week": ["weeks", "week", "w"], | |
| "day": ["days", "day", "d"], | |
| "hour": ["hours", "hour", "hrs", "hr", "h"], | |
| "minute": ["minute", "minutes", "min", "m"], | |
| "second": ["seconds", "seconds", "secs", "sec", "s"] | |
| ] | |
| // Construct a reverse lookup table to go from unit alias => unit kind | |
| var unitKindTable = [String: String]() | |
| for (kind, aliasArray) in timeUnits { | |
| for alias in aliasArray { | |
| unitKindTable[alias] = kind | |
| } | |
| } | |
| // Break input into individual tokens | |
| // This works well for English and other western languages only | |
| let tokens = input.components(separatedBy: " ") | |
| var duration = DateComponents() | |
| // Process each of the tokens found | |
| for (index, element) in tokens.enumerated() { | |
| // Try to find a unit alias in the list of tokens | |
| var unitKind = unitKindTable[element] | |
| if unitKind == nil || index == 0 { | |
| continue | |
| } | |
| // Try to parse the token before the unit as a number | |
| var value = Int(tokens[index - 1]) | |
| if value == nil { | |
| continue | |
| } | |
| // At this point, we've determine the unit type and the quantity | |
| // NSDateComponent doesn't deal with weeks the way we want. | |
| // Remap a week as 7 days | |
| if unitKind == "week" { | |
| unitKind = "day" | |
| value! *= 7 | |
| } | |
| // Set the component value through the extension | |
| duration[unitKind!] = value! | |
| } | |
| return duration | |
| } | |
| print(timeInterval(parsing: "1 h")) | |
| print(timeInterval(parsing: "1 min")) | |
| print(timeInterval(parsing: "1 day")) |
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