interfaces-insight.go

package main

import (
	"fmt"
	"math"
)

// =======================
// The structs' definition
// =======================
type rectangle struct {
	width  float64
	length float64
}

type circle struct {
	radius float64
}

// ========================
// The interface definition
// ========================
type Shape interface {
	findPerimeter() float64
	findArea() float64
}

// ==================================================
// Receiver functions (as specified by the interface)
// ==================================================

// Receiver function for area of circle
func (c circle) findArea() float64 {
	return math.Pi * c.radius * c.radius
}

// Receiver function for area of rectangle
func (r rectangle) findArea() float64 {
	return r.length * r.width
}

// Receiver function for perimeter of circle
func (c circle) findPerimeter() float64 {
	return 2 * math.Pi * c.radius
}

// Receiver function for perimeter of rectangle
func (r rectangle) findPerimeter() float64 {
	return 2 * (r.length + r.width)
}

// ============================================
// The function which brings all the difference
// ============================================
func getProperty(s Shape) {
	fmt.Println("The area is", s.findArea())
	fmt.Println("The perimeter is", s.findPerimeter())
}

// ===================
// The main() function
// ===================
func main() {
	rect := rectangle{
		width:  10.7,
		length: 20.3,
	}
	cir := circle{
		radius: 4,
	}
	fmt.Println("RECTANGLE:")
	getProperty(rect)
	fmt.Println("\nCIRCLE:")
	getProperty(cir)
}