Time formatting and converting from string

Question

I'm quite new to Go and mainly work in C#. I am currently working on something that will be used as a command to get the next bus. Currently it does not compile because I am struggling with understanding how to use the time package in Go.

I have an array of strings formatted as times when it is scheduled and another for the minutes when it is a regular service like so (there are many more times these are just an example:

var ScheduledTimes = []string{"06:34", "06:54", "17:09", "17:19"}
var RegularTimes = []string{"05", "50"}

So what I am currently doing is getting the current time and checking if it is in regular service by doing this:

func isWithinRegularService(check time.Time) bool {
    RegularStart, err := time.Parse(time.Kitchen, "10:05")
    RegularEnd, err := time.Parse(time.Kitchen, "13:52")
    return check.After(RegularStart) && check.Before(RegularEnd)
}

time := time.Now().UTC().Format("15:04")
if isWithinRegularService(time) { }

If it is in regular service, I will then determine what hour needs looking at (i.e this one or is the next service within the next hour)

if time.Minutes < 5 && time.Minutes >= 0 {
    RegularTimes[0] = fmt.Sprintf("%s%s", time.Hour+1, RegularTimes[0])
    RegularTimes[1] = fmt.Sprintf("%s%s", time.Hour+1, RegularTimes[1])
    RegularTimes[2] = fmt.Sprintf("%s%s", time.Hour+1, RegularTimes[2])
    RegularTimes[3] = fmt.Sprintf("%s%s", time.Hour+1, RegularTimes[3])
} else {
    RegularTimes[0] = fmt.Sprintf("%s%s", time.Hour, RegularTimes[0])
    RegularTimes[1] = fmt.Sprintf("%s%s", time.Hour, RegularTimes[1])
    RegularTimes[2] = fmt.Sprintf("%s%s", time.Hour, RegularTimes[2])
    RegularTimes[3] = fmt.Sprintf("%s%s", time.Hour, RegularTimes[3])
}

Before I pass that array to another func to give me the times to check between

type BusTime struct {
betweenStart string
betweenEnd   string
}

func getBusTime(busTimes []array, iteration int) BusTime {

    var timesToReturn BusTime

    if iteration == busTimes.Count()-1 {
        timesToReturn.betweenStart = busTimes[iteration]
        timesToReturn.betweenEnd = busTimes[0]
    } else {
        timesToReturn.betweenStart = busTimes[iteration]
        timesToReturn.betweenEnd = busTimes[iteration+1]
    }

    return timesToReturn
}

busTimes := getBusTime(quaylinkRegularTimes, i)

And lastly I then check if the time provided is between the times to compare:

check.After(start) && check.Before(end)

That is about it for this project. If it is not with regular service it will do the exact same but skip out determining what hour to look at.

Currently this does not build because I am using strings where I should be using times, I was hoping to get some guidance, some examples, and corrections on how to use times correctly to achieve what I'm looking to do. So far I believe my logic to the way this will flow is correct, but I'm stuck getting it to compile.

Answer 1

Since time.Time is a particular instant, at a particular location, using it for arbitrary clock time without a day or timezone can be awkward. What you're really looking for is the duration since 00:00, so a time.Duration makes more sense. You could even use your own type based on minutes since midnight for example, but if you use a time.Duration you'll be able to compose your times with time.Time more easily.

Here's an example function to parse your clock times, and minutes into a time.Duration

func ParseTime(t string) (time.Duration, error) {
    var mins, hours int
    var err error

    parts := strings.SplitN(t, ":", 2)

    switch len(parts) {
    case 1:
        mins, err = strconv.Atoi(parts[0])
        if err != nil {
            return 0, err
        }
    case 2:
        hours, err = strconv.Atoi(parts[0])
        if err != nil {
            return 0, err
        }

        mins, err = strconv.Atoi(parts[1])
        if err != nil {
            return 0, err
        }
    default:
        return 0, fmt.Errorf("invalid time: %s", t)
    }

    if mins > 59 || mins < 0 || hours > 23 || hours < 0 {
        return 0, fmt.Errorf("invalid time: %s", t)
    }

    return time.Duration(hours)*time.Hour + time.Duration(mins)*time.Minute, nil
}

You can also combine this with your own type, using the same underlying int64 type, so that you can easily format the time.Duration and add your own methods. It's up to you if returning a Time or a time.Duration from ParseTime is more convenient. The two here are directly convertible.

type Time int64

func (t Time) Hours() int {
    return int(time.Duration(t) / time.Hour)
}

func (t Time) Minutes() int {
    return int((time.Duration(t) % time.Hour) / time.Minute)
}

func (t Time) String() string {
    return fmt.Sprintf("%02d:%02d", t.Hours(), t.Minutes())
}

You could combine these like so: http://play.golang.org/p/E679m2wlUO