Generic Method Parameters in Golang

Question

I need help with making this work for any type.

I have got a function I need to accept other types that have ID property.

I have tried using interfaces but that did not work for my ID property case. Here is the code:

package main


import (
  "fmt"
  "strconv"
  )

type Mammal struct{
  ID int
  Name string 
}

type Human struct {  
  ID int
  Name string 
  HairColor string
}

func Count(ms []Mammal) *[]string { // How can i get this function to accept any type not just []Mammal
   IDs := make([]string, len(ms))
   for i, m := range ms {
     IDs[i] = strconv.Itoa(int(m.ID))
   }
   return &IDs
}

func main(){
  mammals := []Mammal{
    Mammal{1, "Carnivorious"},
    Mammal{2, "Ominivorious"},
  }

  humans := []Human{
    Human{ID:1, Name: "Peter", HairColor: "Black"},
    Human{ID:2, Name: "Paul", HairColor: "Red"},
  } 
  numberOfMammalIDs := Count(mammals)
  numberOfHumanIDs := Count(humans)
  fmt.Println(numberOfMammalIDs)
  fmt.Println(numberOfHumanIDs)
}

I get this

error prog.go:39: cannot use humans (type []Human) as type []Mammal in argument to Count

See Go Playground for more details here http://play.golang.org/p/xzWgjkzcmH

Answer 1

You can't do precisely what you ask for in Go. Closest way to do things in Go would be something like this as shown in code below:

type Ids interface{
  Id() int
}

func (this Mammal) Id() int{
  return this.ID
} 

func (this Human) Id() int{
  return this.ID
} 


func Count(ms []Ids) *[]string {
...
    IDs[i] = strconv.Itoa(int(m.Id()))
...
}

func main(){
  mammals := []Ids{
    Mammal{1, "Carnivorious"},
    Mammal{2, "Ominivorious"},
  }

  humans := []Ids{
    Human{ID:1, Name: "Peter", HairColor: "Black"},
    Human{ID:2, Name: "Paul", HairColor: "Red"},
  }
  ...
}  

here is the working example