I have a program that displays a numbered list and asks the user to input either a number or name from the list, and loops a block until the user enters "exit", after which it ends.
I want to add a line or two that puts an error message like, "Sorry, I don't seem to understand your request" if the user inputs something that is not on the list (name/number) and is not the word "exit".
I can't seem to figure it out. Any advice? My current code is below.
def start
display_books
input = nil
while input != "exit"
puts ""
puts "What book would you more information on, by name or number?"
puts ""
puts "Enter list to see the books again."
puts "Enter exit to end the program."
puts ""
input = gets.strip
if input == "list"
display_books
elsif input.to_i == 0
if book = Book.find_by_name(input)
book_info(book)
end
elsif input.to_i > 0
if book = Book.find(input.to_i)
book_info(book)
end
end
end
puts "Goodbye!!!"
end
Seems that you should add an elsif statement in this if:
if book = Book.find_by_name(input)
book_info(book)
elsif input != 'exit'
puts "Sorry, I don't seem to understand your request"
end
A good template for an interpreter is to build around Ruby's very capable case statement:
loop do
case (gets.chomp.downcase)
when 'list'
display_books
when /\Afind\s+(\d+)/
if book = Book.find($1.to_i)
book_info(book)
end
when /\Afind\s+(.*)/
if book = Book.find_by_name($1)
book_info(book)
end
when 'exit'
break
else
puts "Not sure what you're saying."
end
end
Although this involves regular expressions, which can be a bit scary, it does give you a lot of flexibility. \A represents "beginning of string" as an anchor, and \s+ means "one or more spaces". This means you can type in find 99 and it will still work.
You can create a whole command-line interface with it if you take the time to specify the commands clearly. Things like show book 17 and delete book 17 are all possible with a bit of tinkering.
Related
How do I put a message (string) for a specific answer (user input) and another message for another answer? For e.g.
puts "Did You Like My Program?"
feedback = gets
if feedback = "Yes"
puts "We're Glad!"
elsif feedback = "No"
puts "We Will Try To Improve!"
end
What should I change, add, or modify?
Your problem is that, when you compare, you have to use ==, not =.
When you input on command line, you always use Enter. It produces \n at the end of the string. So you need to remove it with chomp.
Also, to filter user input, I suggest this variant:
feedback = nil
until %w[y n].include?(feedback)
puts 'Did You Like My Program? Y/N'
feedback = gets.chomp.downcase
end
if feedback == 'y'
puts "We're Glad!"
else
puts "We Will Try To Improve!"
end
Brief explanation:
The code uses Array#include? and String#downcase.
%w[y n] is equal to ["y", "n"].
The until-loop executes the code while the condition is false.
If this code executes the else statement, I want it to retry either from rescue or from begin.
Running the code asks me for an input and, when I input it, the code doesn't work.
1- What can I do to make this code work with the else statement running the retry?
2- Why does removing rescue create a retry Syntax Error?
# Creates input method
def input
x = gets.to_i
end
#Begins the first choice
begin
puts "What will you do?
1- Get a closer look
2- Go in the opposite direction
Write your input an press enter:"
rescue
#Calls input method
choice = input
if choice == 1
puts "You get a closer look and..."
elsif choice == 2
puts "You go in the opposite direction, out of trouble"
else
puts "Incorrect input, enter a number between the one's avaliables:"
end
#Retries if the choice is error
retry if choice != 1||2
end
Using a rescue block is for handling exceptions, I really don't think it's needed here. A loop will do the job.
puts "What will you do?",
"1- Get a closer look",
"2- Go in the opposite direction",
"Write your input and press enter:"
loop do
choice = gets.to_i
if choice == 1
puts "You get a closer look and..."
break
elsif choice == 2
puts "You go in the opposite direction, out of trouble"
break
else
puts "Incorrect input, enter a number between the ones available:"
end
end
I am a beginner who is trying to learn Ruby. I have learned some of the easier stuff so far, but I seem to be stuck in trying to combine a couple of things I've learned.
What I am trying to do is to ask the user a question and tell them to enter either 1 or 2. A simple if statement would let me respond with one option if they enter 1, and another option if they enter 2. However, if they enter something entirely different like a different number, a string, etc., how can I prompt them to try again and have it loop back to the original question?
What I have so far looks something like this.
prompt = "> "
puts "Question asking for 1 or 2."
print prompt
user_input = gets.chomp.to_i
if user_input == 1
puts "One response."
elsif user_input == 2
puts "Second response."
else
puts "Please enter a 1 or a 2."
end
This is where I'm stuck. How do I make it go back to the "Question asking for 1 or 2." until the user enters a 1 or 2? I know it's probably a loop of some kind, but I can't seem to figure out which kind to use and how to incorporate asking for user input repeatedly (if necessary) until getting the desired input. Any help would be greatly appreciated. Thanks.
You're right that you need to run your code in a loop. Using a while loop with gets.chomp as a condition, you can carry on asking for user input until you decide you've got what you want.
In this case, you want to validate the answer to the question and ask again if it's invalid. You don't need to change a great deal, except making sure you break out of the loop when the answer is correct. If the answer is wrong, print the prompt again.
This is a slightly refactored version that uses case instead, but it shows what you need to do. There is no doubt a cleaner way to do this...
prompt = "> "
puts "Question asking for 1 or 2."
print prompt
while user_input = gets.chomp # loop while getting user input
case user_input
when "1"
puts "First response"
break # make sure to break so you don't ask again
when "2"
puts "Second response"
break # and again
else
puts "Please select either 1 or 2"
print prompt # print the prompt, so the user knows to re-enter input
end
end
Try using the until method like this:
prompt = "> "
print prompt
user_input = nil
until (user_input == 1 or user_input == 2)
puts "Please enter a 1 or 2."
user_input = gets.chomp.to_i
end
if user_input == 1
puts "One response."
elsif user_input == 2
puts "Second response."
else
puts "Please enter a 1 or a 2."
end
user_input = 0
until [1,2].include? user_input do
puts "Please enter a 1 or a 2.>"
user_input = gets.chomp.to_i
end
if user_input == 1
puts "One response."
else
puts "Second response."
end
You can try this to make your code clean.
While the title of this question is somewhat unrelated, please see the trick that is used here: Ruby Retry and ensure block is not working
The use of error detection and unique retry keyword available in Ruby allows you to easily do a retry-loop compacted together with nice an error handling.
However, mind that the example I pointed is not really the best. There are some minor issues. For example, you should not catch Exception, rather simple rescue => e would be enough. But the overall idea should be rather clear.
I am trying to make a number guessing game in Ruby but the program exits after I type in yes when I want to play again. I tried using the catch and throw but it would not work. Could I please get some help.
Here is my code.
class Game
def Play
catch (:start) do
$a=rand(11)
puts ($a)
until $g==$a
puts "Guess the number between 0-10."
$g=gets.to_i
if $g>$a
puts "The number you guessed is too high."
elsif $g==$a
puts "Correct you won!!!"
puts "Would you like to play again?"
$s=gets()
if $s=="yes"
$c=true
end
if $c==true
throw (:start)
end
elsif $g<$a
puts "The number you guessed is too low."
end
end
end
end
end
Game.new.Play
Edit: Here's my new code after trying suggestions:
class Game
def Play
catch (:start) do
$a=rand(11)
puts ($a)
while $s=="yes"
until $g==$a
puts "Guess the number between 0-10."
$g=gets.chomp.to_i
if $g>$a
puts "The number you guessed is too high."
elsif $g==$a
puts "Correct you won!!!"
puts "Would you like to play again?"
$s=gets.chomp
if $s=="yes"
throw (:start)
end
elsif $g<$a
puts "The number you guessed is too low."
end
end
end
end
end
end
Game.new.Play
Your first problem is here:
$s=gets()
if $s=="yes"
$c=true
end
The gets method will read the next line including the new line character '\n', and you compare it to only "yes":
> gets
=> "yes\n"
The idiomatic way to fix this in Ruby is the chomp method:
> gets.chomp
=> "yes"
That said, your code has two other deficiencies.
You may come from a language such as PHP, Perl, or even just Bash scripting, but Ruby doesn't require the dollar sign before variables. Using a $ gives a variable global scope, which is likely not what you want. In fact, you almost never want a variable to have global scope.
Ruby uses three types of symbol prefixes to indicate scope - # for instance, ## for class, and $ for global. However the most common type of variable is just local which doesn't need any prefix, and what I would suggest for your code.
I have always been told that it is very bad practice to use exceptions for control structure. Your code would be better served with a while/break structure.
When you do gets(), it retrieves the full line with a '\n' in the end. You need to trim the new line character by using:
$g=gets.chomp.to_i
Same for other gets
Based on your updated code (where you fixed the newline problem shown by others), your new problem is that you have wrapped all your game inside while $s=="true". The very first time your code is run, $s is nil (it has never been set), and so you never get to play. If you used local variables instead of global variables (s instead of $s) this would have become more obvious, because the code would not even have run.
Here's one working way that I would re-write your game.
class Game
def play
keep_playing = true
while keep_playing
answer = rand(11) # Make a new answer each time
puts answer if $DEBUG # we don't normally let the user cheat
loop do # keep going until I break from the loop
puts "Guess the number between 0-10."
guess = gets.to_i # no need for chomp here
if guess>answer
puts "The number you guessed is too high."
elsif guess<answer
puts "The number you guessed is too low."
else
puts "Correct you won!!!",
"Would you like to play again?"
keep_playing = gets.chomp.downcase=="yes"
break
end
end
end
end
end
Game.new.play
I know this doesn't really answer your question about why your code isn't working, but after seeing the code you posted I just had to refactor it. Here you go:
class Game
def initialize
#answer = rand(11)
end
def play
loop do
guess = get_guess
display_feedback guess
break if guess == #answer
end
end
def self.play_loop
loop do
Game.new.play
break unless play_again?
end
end
private
def get_guess
puts "Guess the number between 0-10."
return gets.chomp.to_i
end
def display_feedback(guess)
if guess > #answer
puts "The number you guessed is too high."
elsif guess < #answer
puts "The number you guessed is too low."
elsif guess == #answer
puts "Correct you won!!!"
end
end
def self.play_again?
puts "Would you like to play again?"
return gets.chomp == "yes"
end
end
Game.play_loop
I'm curious if there's a way to have the program go back up the if statement stack?
Ideally, the program would return to line 2 and prompt the user for the input variable, then continue to evaluate like it did the first time. Think of it like a cursor in a text editor, I just want to move it from either of those two comments back up to line 2. The two places of interest are commented out below:
while true
input = gets.chomp
if input != input.upcase
puts "HUH?! SPEAK UP, SONNY!"
elsif input == 'BYE'
puts "HUH?! SPEAK UP, SONNY!"
input = gets.chomp
if input == 'BYE'
puts "HUH?! SPEAK UP, SONNY!"
input = gets.chomp
if input == 'BYE'
puts "GOOD BYE!";
break
else
# return to top-level if statement
end
else
# return to top-level if statement
end
else
random_year = rand(1930..1950)
puts "NO, NOT SINCE #{random_year}!"
end
end
In the code you show, you don't need to do anything to make the flow of execution go back to line 2. Just omit the else clauses in the two places you marked. The flow of execution will drop down to the bottom of the while loop, then loop back to the top, then go back to line 2.
You need to use a while statement to set a condition flag and check it, which will loop back to the while statement if you don't change the flag:
flag = 0
while flag1 == 0
if var = "string"
then ...statements...
flag1 = 1 ; this allows us to break out of this while loop
else ...statements...
end
end
If flag1 is not 0 at the end of the while statement, the while statement will loop back. For two such conditions, you need to nest the while loops. You might have to re-order your statements to make multiple while loops work this way.
You can avoid this level of neasted ifs with:
byecount = 0
while byecount < 3
input = gets.chomp
if input == "BYE"
byecount += 1
next
else
byecount = 0
end
if input != input.upcase
puts "HUH?! SPEAK UP, SONNY!"
else
puts "NO, NOT SINCE #{rand(1930..1950)}!"
end
end
puts "GOOD BYE!"
Or you can write a catch..throw flow structure. (Really.. if you need to use it, something is wrong with your design)
catch :exitloop do
while ...
if ...
if ...
if ...
throw :exitloop
end
end
end
end
end
Here's how I'd write a similar exercise:
BYE = 'BYE'
HUH = "HUH?! SPEAK UP, SONNY!"
loop do
input = gets.chomp
if input != input.upcase
puts HUH
next
end
if input != BYE
random_year = rand(1930..1950)
puts "NO, NOT SINCE #{random_year}!"
next
end
puts HUH
input = gets.chomp
if input == BYE
puts HUH
input = gets.chomp
if input == BYE
puts "GOOD BYE!";
break
end
end
end
I used loop instead of while. Matz, the main man for Ruby, recommends loop. See "Is there a “do … while” loop in Ruby?" for further discussion about it.