Go Language: Interfaces

Interfaces are collection of method signatures.

‘interface’ keyword is used to create interfaces.

Example

type Details interface {

         aboutMe()

         id() int

}

How can a type implement an interface?

You just need to implement all the methods in the interface (You even no need to explicitly specify that you are implementing an interface, you just write the implementation, this is called duck typing.).

For example, Employee type implements Details interface.

type Employee struct {

         name string

         id   int

}

func (emp *Employee) aboutMe() {

         fmt.Println("name : ", emp.name, ", id : ", emp.id)

}

func (emp *Employee) getId() int {

         return emp.id

}

If you define ‘printMyDetails’ method by adding Details object as an argument, you can pass any object of type ‘T’ that implements Details interface.

func printMyDetails(obj Details) {

         obj.aboutMe()

}

In Go, if your type implements all the methods of the interface, then your type can be stored in a value of interface type. For example, Details object can store Employee object.

emp1 := &Employee{"Krishna", 123}

printMyDetails(emp1)

App.go

package main

import (
 "fmt"
)

type Details interface {
 aboutMe()
 getId() int
}

type Employee struct {
 name string
 id   int
}

func (emp *Employee) aboutMe() {
 fmt.Println("name : ", emp.name, ", id : ", emp.id)
}

func (emp *Employee) getId() int {
 return emp.id
}

func printMyDetails(obj Details) {
 obj.aboutMe()
}

func main() {
 emp1 := &Employee{"Krishna", 123}

 printMyDetails(emp1)
}

Output

name :  Krishna , id :  123

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