Dot Baiki wrote:
Hey! Amazing quick response! Outstanding. Sweet solutions! Will continue
reading my books I bought. Really cool. Thanks so much. This is what I
made now:
— begin —
#!/usr/bin/env ruby
class AreaOfCircle
PI = 3.14159265
def initialize(radius)
@radius = radius
@area = nil
end
def calc_area(radius)
@area = PI * @radius**2
end
end
print 'Enter radius of circle: ’
radius = gets.to_f
puts “You entered: #{radius}”
instance = AreaOfCircle.new(radius)
screen_output = instance.calc_area(radius)
puts “Result: #{screen_output}”
— end —
You know, the cool thing is that I really soooooon will understand Ruby
and its beauty 
Baiki
Baiki,
I think you might end up getting surprised by what happens when you do
this. For instance, consider the results of the following code, given
your existing AreaOfCircle class (of which I really dislike the name,
but never mind that for now):
circle = AreaOfCircle.new 5 # circle has @radius=5, @area=nil
area = circle.calc_area 3 # assigns @area=78.540… (25*PI), i.e.
the radius
# parameter is completely ignored
So get rid of the completely unnecessary parameter for calc_area.
Furthermore, the user probably doesn’t want to have to remember to
manually call for the area to be calculated when he creates a circle, so
just do that in your constructor. Add accessors for @radius and @area
and you’re really cookin’. It might look something like this:
class MyCircle
attr_accessor :radius, :area
PI = 3.14159265
def initialize(radius)
@radius = radius
calc_area
end
def calc_area
@area = PI * @radius**2
end
end
Your program code could then look like this:
print 'Enter radius of circle: ’
radius = gets.to_f
puts “You entered: #{radius}”
instance = MyCircle.new(radius)
screen_output = instance.area
puts “Result: #{screen_output}”
On the other hand, if all you’re interested in is calculating the area
and you don’t actually need to store the information, use a mixin
instead of a full-blown class:
Module AreaOfCircle
PI = 3.14159265
def calc_area(radius)
PI * radius**2
end
end
begin program code
include AreaOfCircle
print 'Enter radius of circle: ’
radius = gets.to_f
puts “You entered: #{radius}”
screen_output = calc_area radius
puts “Result: #{screen_output}”
I know I threw a lot of stuff at you, so feel free to ask about anything
you don’t understand there.
Doug