LSP_Good_post.swift

protocol Field {
	var area: Float { get }
}

class RectangleField: Field {
        
	var width: Float = 0
	var height: Float = 0
	var area: Float {
		return width * height
	}
	
}

class SquareField: Field {
	
	var side: Float = 0
	var area: Float {
		return side * side
	}
	
}

func printField(field: Field) {
	print(field.area)
}

let field = RectangleField()
field.width = 2
field.height = 4
printField(areable: field) // 8

let squareField = SquareField()
squareField.side = 2
printField(areable: squareField) // 4