Usage of interface in Go

Question

I would like to understand the interface type with a simple example of it\'s use in Go (Language).

I read the web documentation, but I don\'t get it.

Answer 1

In this example, I'm using the interface to demonstrate how to achieve polymorphism in Golang.

package main 


import(
    "fmt"
    "math"
)

func main(){
    rect := Rectangle{20,50}
    cir := Circle{2}

    //According to object you passed in getArea method, 
    // it will change the behaviour and that is called Polymorphism.
    fmt.Println("Area of Rectangle =",getArea(rect))
    fmt.Println("Area of Circle =",getArea(cir))

}

//Interface Shape with one area method
type Shape interface{
     area() float64
}

//Creating Rectangle and Circle type using struct 
type Rectangle struct{
    height float64
    width float64
}

type Circle struct{
    radius float64
}

//Receiver function, which implements struct's area methods
func(r Rectangle) area() float64{
    return r.height * r.width
}

func(c Circle) area() float64{
    return math.Pi * math.Pow(c.radius,2)
}

//passing interface as arguments, which can calculate shape of any mentioned type
//All the struct are tied together because of the Interface.
func getArea(shape Shape) float64{
    return shape.area()
}