Creating a loop within an if/else statement

Question

I'm in the early stages in learning Ruby and ran into an issue when trying to create a conditional statement for one of my programs. I basically wanted it to loop back and grab a fresh input value if the orignal didn't meet the criteria of the first two conditionals.

So for example:

puts "Choose either the 'red' or 'blue' pill"

choice = gets.to_s.downcase.chomp

if choice == red
    puts "Fasten your seatbelt dorothy 'cause kansas is going bye-bye" 
elsif choice == "blue"
   puts "The story ends, you wake up in your bed and believe whatever you want to believe"
else
    puts "You have to choose one"
end

Is red a variable? If not, choice == red will fail. It's important your source code be runnable. — the Tin Man
– the Tin Man, Commented Feb 21, 2014 at 18:59

Cary Swoveland · Accepted Answer · 2014-02-21 23:11:13Z

3

Here's another common construct:

loop do
  puts "Choose either an 'upper' or a 'downer'"

  case gets.downcase.chomp
  when "upper"
    puts "Fasten your seatbelt dorothy 'cause kansas is going bye-bye"
    break 
  when "downer"
    puts "The story ends, you wake up and believe whatever you want to believe"
    break
  else
    puts "You have to choose one"
  end
end

edited Feb 21, 2014 at 23:11

answered Feb 21, 2014 at 19:03

Cary Swoveland

111k6 gold badges69 silver badges105 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Arup Rakshit Over a year ago

Nice use-case of using #loop here. But gets.to_s.downcase.chomp can be written as gets.downcase.chomp.

Cary Swoveland Over a year ago

Thanks, @Arup, I just blindly cut-and-pasted. Shame on me! Will fix.

usha · Accepted Answer · 2014-02-21 17:49:48Z

1

begin
  puts "Choose either the 'red' or 'blue' pill"
  choice = gets.to_s.downcase.chomp

  if choice == "red"
    puts "Fasten your seatbelt dorothy 'cause kansas is going bye-bye" 
  elsif choice == "blue"
    puts "The story ends, you wake up in your bed and believe whatever you want to believe"
  else
    puts "You have to choose one"
    choice = "invalid"
  end
end while(choice == "invalid")

console output:

Choose either the 'red' or 'blue' pill
#empty input
You have to choose one
Choose either the 'red' or 'blue' pill
red
Fasten your seatbelt dorothy 'cause kansas is going bye-bye
 => nil

edited Feb 21, 2014 at 17:49

answered Feb 21, 2014 at 17:38

usha

29.4k5 gold badges75 silver badges94 bronze badges

5 Comments

Linuxios Over a year ago

There is no such method as String#blank?. Even if there was, this doesn't work right.

DGM Over a year ago

blank? is a rails thing.

usha Over a year ago

@DGM yes, blank? is rails. I changed it.

Carl Edwards Over a year ago

I see what you did. What if I said "green"? Having the user input a value not listed is what I was looking for.

BroiSatse Over a year ago

add choice = nil under else statement and change choice.empty? to choice.

Arup Rakshit · Accepted Answer · 2014-02-21 17:58:34Z

How about Ruby's throw and catch for this scenario :

def ask
  puts "Choose either the 'red' or 'blue' pill"
  choice = gets.downcase.chomp
  if choice == 'red'
    puts "Fasten your seatbelt dorothy 'cause kansas is going bye-bye" 
  elsif choice == "blue"
    puts "The story ends, you wake up in your bed and believe whatever you want to believe"
  else
    puts "You have to choose one"
    throw :done,ask
  end
end

catch(:done) do
  ask
end

Lets run the code :

(arup~>Ruby)$ ruby -v a.rb
ruby 2.0.0p0 (2013-02-24 revision 39474) [i686-linux]
Choose either the 'red' or 'blue' pill
foo
You have to choose one
Choose either the 'red' or 'blue' pill
bar
You have to choose one
Choose either the 'red' or 'blue' pill
blue
The story ends, you wake up in your bed and believe whatever you want to believe
(arup~>Ruby)$

BroiSatse · Accepted Answer · 2014-02-21 17:52:15Z

0

class WrongChoice < StandardError
end

puts "Choose either the 'red' or 'blue' pill"

begin
  choice = gets.to_s.downcase.chomp
  raise WrongChoice.new unless ['blue', 'red'].include? choice 
  if choice == red
    puts "Fasten your seatbelt dorothy 'cause kansas is going bye-bye" 
  else 
   puts "The story ends, you wake up in your bed and believe whatever you want to"
  end
rescue WrongChoice
  puts "You have to choose one"
  retry
end

edited Feb 21, 2014 at 17:52

answered Feb 21, 2014 at 17:41

BroiSatse

44.8k8 gold badges63 silver badges89 bronze badges

1 Comment

Linuxios Over a year ago

While I wouldn't use an exception for this, the retry is very elegant.

Collectives™ on Stack Overflow

Creating a loop within an if/else statement

4 Answers 4

2 Comments

5 Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

5 Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related