Golang : Fix - does not implement sort.Interface (missing Len method)


You are trying to use the sort.Sort() or sort.Reverse() functions on type []string data but encounter this error message:

cannot use strSlice (type []string) as type sort.Interface in argument to sort.Sort: []string does not implement sort.Interface (missing Len method)

What's going on and how to fix this?


Cast the []string slice/array to type StringSlice or if you are dealing integer or float - cast to IntSlice or Float64Slice type first before using the sort.Sort() function.

To cast/convert the []string slice/array, use sort.StringSlice() function.

For example:

 package main

 import (

 func main() {
 str := "Dog,Apple,Cat,Boy"

 strSlice := strings.Split(str, ",")

 fmt.Println("Before : ", strSlice)

 sortableStrSlice := sort.StringSlice(strSlice) <------- here!


 fmt.Println("After : ", sortableStrSlice)


Before : [Dog Apple Cat Boy]

After : [Apple Boy Cat Dog]

Happy coding!

  See also : Golang : Reverse IP address for reverse DNS lookup example

By Adam Ng

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