interface_example.go

package main

import "fmt"

func main() {
	// Create a new concrete IP of type `fileIP`, and populate with two tags
	aFileIp := &fileIp{tags: map[string]string{"name": "Rolf", "likes": "Coffee"}}

	// Call the function printTags(), which takes the interface `IP`
	printTags(aFileIp)
}

// Function that takes the *interface* `IP`, and calls methods of the interface
func printTags(ip IP) {
	fmt.Println("Tags:")
	for tagName, tagValue := range ip.GetTags() {
		fmt.Println("Tag name: ", tagName)
		fmt.Println("Tag value:", tagValue, "\n")
	}
}

// The IP interface
type IP interface {
	GetTags() map[string]string
	GetTag(tagName string) string
	SetTag(tagName string, tagValue string)
}

// A concrete IP type, fulfilling the IP interface
type fileIp struct {
	tags map[string]string
}

func (ip *fileIp) GetTags() map[string]string {
	return ip.tags
}
func (ip *fileIp) GetTag(tagName string) string {
	return ip.tags[tagName]
}
func (ip *fileIp) SetTag(tagName string, tagValue string) {
	ip.tags[tagName] = tagValue
}