Range over element of interface implementation

Question

Let's supposed I've got the following interface and two structs that implement it:

type Tmp interface {
    MyTmp() string
}

type MyStructA struct {
    ArrayOfItems   []int
}

func (a MyStructA) MyTmp() string {
    return "Hello World"
}

type MyStructB struct {
    ArrayOfItems   []int
}

func (a MyStructB) MyTmp() string {
    return "Hello World B"
}

As you notice both MyStructA and MyStructB implement Tmp and both have a property named ArrayOfItems. Using the interface signature, how could I iterate over that property which both have? Something similar to:

func (c ADifferentStruct) iterate(myTmp Tmp) {

   for _, number := range myTmp.ArrayOfItems {
      fmt.Println(number)
   }
}

NOTE: I don't want to add another method to the interface (ie getter/setters) to process or to define ArrayOfItems

is this possible?

Add method `Items() []int` to `Tmp` and implement the method on the two struct types. Call `Items` in `iterate`. — Charlie Tumahai, Aug 12 '20 at 02:31
You can find a possible answer and a good discussion here: https://stackoverflow.com/questions/26027350/go-interface-fields — pacuna, Aug 12 '20 at 03:49

score 0 · Answer 1 · answered Aug 12 '20 at 14:38

You need a method to return those items...

see this: https://play.golang.org/p/rnH0riWKqRY


package main

import "fmt"

type Tmp interface {
    MyTmp() string
    Items() []int
}

type MyStructA struct {
    ArrayOfItems []int
}

func (a MyStructA) MyTmp() string {
    return "Hello World"
}

func (a MyStructA) Items() []int {
    return a.ArrayOfItems
}

type MyStructB struct {
    ArrayOfItems []int
}

func (a MyStructB) MyTmp() string {
    return "Hello World B"
}

func (a MyStructB) Items() []int {
    return a.ArrayOfItems
}

func iterate(tmp Tmp) {
    for _, val := range tmp.Items() {
        fmt.Println(val)
    }
}

func main() {
    a := MyStructA{[]int{1, 2, 3}}
    b := MyStructA{[]int{-1, -2, -3}}
    iterate(a)
    iterate(b)

}

Range over element of interface implementation

1 Answers1