SOLID: Open-Closed Principle `ideal`

idealImplShapes.go

package main

import (
	"fmt"
	"math"
)

type geometry interface {
	// Area of a shape
	area() float64
	// Name of shape
	name() string
}

// For our example we'll implement this interface on
// `rect` and `circle` types.
type rect struct {
	width, height float64
}

func (r rect) area() float64 {
	return r.width * r.height
}

func (r rect) name() string {
	return "Rectangle"
}

type circle struct {
	radius float64
}

func (c circle) area() float64 {
	return math.Pi * c.radius * c.radius
}

func (c circle) name() string {
	return "Circle"
}

func measure(g geometry) {
	fmt.Println(g.name())
	fmt.Println(g.area())
}

func main() {
	r := rect{width: 3, height: 4}
	c := circle{radius: 5}

	measure(r)
	measure(c)
}