interfaces_code_snippet_18.go

type car struct {}

func (c *car) start() { return }
func (c *car) stop() { return }
func (c *car) recycle() { fmt.Println("Recycling...") }

type vehicle interface {
	start()
	stop()
}

type recyclable interface {
	recycle()
}

func main() {
	var v vehicle = new(car)
	
	if r, ok := v.(recyclable); ok {
		// In the scope of this code block, we've now asserted that v satisfies the recyclable interface.
		// Therefore, we can call recycle() on it!
		r.recycle() // Prints "Recycling..."
	}
	
	// v.recycle() // <- This is not possible! In the outer code block, we know that v is a vehicle,
	// but the assertion applies only to the code block containing r. Here, v is still just a vehicle.
}