You can easily check if a key exists in a go map by using the ok result:
value, ok := myMap[key]
Or in an one line check:
if val, ok := myMap[key]; ok {
// do something
}
Tag: kb
Golang: Reverse ISOWeek, get the date of the first day of ISO week
If you work with weeknummers, you can find the weeknumber of a date with the Golang function time.ISOWeek. However you wish to get the first date of a week, there is no such function in Google Go. So let’s write it our selfs:
func FirstDayOfISOWeek(year int, week int, timezone *time.Location) time.Time {
date := time.Date(year, 0, 0, 0, 0, 0, 0, timezone)
isoYear, isoWeek := date.ISOWeek()
// iterate back to Monday
for date.Weekday() != time.Monday {
date = date.AddDate(0, 0, -1)
isoYear, isoWeek = date.ISOWeek()
}
// iterate forward to the first day of the first week
for isoYear < year {
date = date.AddDate(0, 0, 7)
isoYear, isoWeek = date.ISOWeek()
}
// iterate forward to the first day of the given week
for isoWeek < week {
date = date.AddDate(0, 0, 7)
isoYear, isoWeek = date.ISOWeek()
}
return date
}
Golang: measure time to execute code
Sometimes you want to know how long it takes to execute a piece of code. This is how to do it Golang:
func main() {
start := time.Now()
// Do something time consuming
elapsed := time.Since(start)
log.Printf(“Time to execute code %s”, elapsed)
}
Golang create directory
Creating a directory from Google Go is simple with the “os” package. See the example below.
Golang create directory example
path := "/folder/to/create"
err := os.MkdirAll(path,0711)
if err != nil {
log.Println("Error creating directory")
log.Println(err)
return
}
Golang html/template range: access out of loop variable
When you use range in a Golang html/template the “.” variable changes to the current object from the range. We can however still access to old “.” variable with “$”:
{{range $index, $emp := .employees}}
{{ $emp.name }}
{{ msg $ "btn_show" }}
{{ end }}
Golang substr or substring equivalent
Strings are slices in Google Go, so there is really no need for a Golang substr function. For example if you would want to get the first 10 characters of a string:
dt := "2015-01-01 15:45:12"
d := dt[0:10]The resulting value in d will be: “2015-01-01”.
