Bicycle2 refactors Bicycle

bicycle.rb

#!/opt/local/bin/ruby1.9
include Math

class Bicycle
  attr_accessor :wheel_size, :chainring, :cassette, :name

  # Create the object
  def initialize(name = "A Bicycle",wheel_size=27,chainring=42,cassette=[28,24,21,18,16,14,12,11])
    @name = name
    @wheel_size=wheel_size
    @chainring=chainring
    @cassette=cassette
    @gear_i=0
  end

  # change gear
  def set_gear(gear=1)
    @gear_i=gear-1
  end

  # speed based on cadence
  def mph(cadence)
    # this may be imprecise/wrong so don't take my word for it....
    # BTW 63360 is the number of inches in a mile
    return cadence*Math::PI*@wheel_size*(@chainring/@cassette[@gear_i])*60/63360
  end

  def info
      puts "Information for: #{@name}"
      puts "This bicycle has the following characteristics:"
      puts "Wheel size: #{@wheel_size} inches"
      puts "Front gear has #{@chainring} teeth"
      puts  "Rear gears have #{@cassette} teeth"
      puts  "At a cadence of 100 rpm this bike can go approximately #{self.mph(100)} mph in gear #{1+@gear_i}"
    end
end


if __FILE__ == $0
  bike=Bicycle.new
  bf_tikit=Bicycle.new("my bike",16.375,53,[28,24,21,18,16,14,12,11])
  
  bike.set_gear(8)
  bf_tikit.set_gear(8)
  puts ""
  # need to learn how to format to the console some day...
  puts bf_tikit.mph(80)
  puts bike.mph(80)
  
  puts ""
  puts bike.info
  puts bf_tikit.info
  
  
end

bicycle2.rb

#!/opt/local/bin/ruby1.9
include Math

# still has a bit of an odor...

class Bicycle
  attr_accessor :wheel_size, :chainring, :cassette, :name

  # Create the object
  def initialize(arg={name: "A Bicycle",wheel_size: 27,chainring: 42,cassette: [28,24,21,18,16,14,12,11]})
    @name = arg[:name]
    @wheel_size=arg[:wheel_size]
    @chainring=arg[:chainring]
    @cassette=arg[:cassette]
    @gear_i=0
  end

  # change gear
  def set_gear(gear=1)
    @gear_i=gear-1
  end

  # speed based on cadence
  def mph(cadence)
    # this may be imprecise/wrong so don't take my word for it....
    # BTW 63360 is the number of inches in a mile
    cadence*Math::PI*@wheel_size*(@chainring/@cassette[@gear_i])*60/63360
  end

  def info
puts %{
Information for: #{@name}
This bicycle has the following characteristics:
Wheel size: #{@wheel_size} inches
Front gear has #{@chainring} teeth
Rear gears have #{@cassette} teeth
}
# How horrible is this --- mixing puts-ing a string and printf! Gross.
  printf("At cadence of 100 rpm this bike can go approximately %.1f mph in gear %2d", self.mph(100), 1+@gear_i)

    end
end


if __FILE__ == $0
  bike=Bicycle.new
  bf_tikit=Bicycle.new({name: "my bike",wheel_size: 16.375,chainring: 53, cassette: [28,24,21,18,16,14,12,11]})
  
  bike.set_gear(8)
  bf_tikit.set_gear(8)
  puts ""
  # need to learn how to format to the console some day...
  # You would think that someone would have devised a more intuitive way to format stuff by now. 
  # printf goes back to Fortan, COBOL and the stone ages...
  #
  printf("Bike Friday can go about %.1f mph at a cadence of 80.\n", bf_tikit.mph(80))
  # and I am pretty sure that this is not Ruby-like... but I couldn't find any thing else for the time being...
  printf("Regular bike can go about %.1f mph at a cadence of 80.\n", bike.mph(80))
  
  puts ""
  puts bike.info
  puts bf_tikit.info
  
  
end

Well all you have to do is yank that puts and printf completely out of the info method you are good to go. let the puts outside of your class definition handle everything like it is..
puts bike.info # this does it all. Always remember you may always monkey patch the #to_s method:
def to_s
%{ string content here }
end
And call
puts bike # and get the same result. #to_s will get called on an object when it is being "PUTSed" less typing even.

Not if I want the numbers to be formatted. maybe there is another way to create a formatted string from a float/integer? In which case I could catenate the formatted numbers into the string when I create it in info, and, as you suggest, do the putsing outside (which I agree is MUCH cleaner and more flexible) printf itself returns nil, so you cant capture the result and then use it.

…

On Mar 16, 2011, at 1:41 AM, snuggs wrote: Well all you have to do is yank that puts and printf completely out of the info method you are good to go. let the puts outside of your class definition handle everything like it is.. puts bike.info # this does it all. Always remember you could really just do the following: def to_s %{ string content here } end And call puts bike # and get the same result. .to_s will get called on an object when it is being "PUTSed" less typing even. ## Reply to this email directly or view it on GitHub: https://gist.github.com/864265

OK I got it. sprintf returns a string. There is also a method called format that is synonymous with sprintf, if that looks better for readability...

 def info
%{
Information for: #{@name}
This bicycle has the following characteristics:
Wheel size: #{@wheel_size} inches
Front gear has #{@chainring} teeth
Rear gears have #{@cassette} teeth
#{sprintf("At cadence of 100 rpm this bike can go approximately %.1f mph in gear %2d", self.mph(100), 1+@gear_i)}
}
 end

or
#{format("At cadence of 100 rpm this bike can go approximately %.1f mph in gear %2d", self.mph(100), 1+@gear_i)}
for the last line of info

FYI puts returns nil as well hence why it's an "anti-pattern" to call puts in a method ESPECIALLY as the last statement in a method. Why return nil if you get an implicit return for free? Usually you return nil ONLY when you explicitly want the return to be nil.

When it comes to formatting floats there is an easier way....

1. you can call to_s on the float and now it's a string that can be formatted or...
2. the % operator on strings.
   "%5.1f" % 345.6789 # "345.7"
   "%05d" % 123 # "00123"
   "%-5s" % "ID" # "ID "
   "%04x" % 0xfc14 # "fc14"
   "%6.2f, %05d" % [345.6789,123] # "345.68, 00123"