I'm trying to make a text editor in Ruby, but I don't know how to memorize an input with gets.chomp.
Here is my code so far:
outp =
def tor
text = gets.chomp
outp = "#{outp}" += "#{text}"
puts outp
end
while true
tor
end
Ordinary variables , like outp, in a method are only visible (AKA have scope) inside that method.
a = "aaa"
def x
puts a
end
x # =>error: undefined local variable or method `a' for main:Object
Why is that? For one thing, if you are writing a method and you need a counter, you can use a variable named i (or whatever) without worrying about other variables named i outside your method.
But... you want to interact with an outside variable in your method! This is one way:
#outp = "" # note the "", initializing #output to an empty string.
def tor
text = gets.chomp
#outp = #outp + text #not "#{#output}"+"#{text}", come on.
puts #outp
end
while true
tor
end
The # gives this variable a greater visisbility (scope).
This is another way: pass the variable as an argument. It is as saying to your method: "Here, work with this.".
output = ""
def tor(old_text)
old_text + gets.chomp
end
loop do #just another way of saying 'while true'
output = tor(output)
puts output
end
Related
I have a code below:
secret_number = 8
user_input = ""
def number_guesser(user_input)
while user_input != secret_number
puts "Guess a number between 1 and 10:"
user_input = gets.chomp
if user_input != secret_number
puts "Wrong! Try again."
else
puts "You guessed correctly!"
end
end
end
number_guesser(user_input)
when I tried to run the above program it showed as below:
****undefined local variable or method secret_number' for main:Object
(repl):211:innumber_guesser'
(repl):221:in `'****
Any ideas?
You can't use a local variable like that inside another scope such as a method, it's two different contexts. Instead you need to pass that in if you want to use it.
It's a simple change:
def number_guesser(user_input, secret_number)
# ...
end
Then just feed that argument in.
You'll note that user_input isn't really necessary as a parameter, you can always initialize and use that locally, so it's actually pointless as an argument.
The pattern to use in that case:
loop do
input = gets.chomp
# Prompting...
break if input == secret_number
# Guessed wrong...
end
The below combined programs should ask for a number remove the first digit (lets call this new number x) and then compute x % 7. Ex: (1121546 % 7) = 5
This all appears to be working except that the number entered in will always compute to 0. modulo_7.rb works by itself and will print the correct outcome when passed a parameter.
The question is am I not passing the variables/ parameters properly or is there something else that is getting in the way?
class Number_check_interface
def get_cert_number
print "You are about to check receive the check number for a policy/cert id."
#cert_id = nil
until #cert_id.is_a?(Fixnum) do
puts " Enter the policy/cert ID. "
begin
#cert_id = Integer(gets)
rescue ArgumentError
end
end
end
end
class Run_number_check_interface
def run
load 'modulo_7.rb'
n = Number_check_interface.new
n.get_cert_number
checking_policy_number = Get_policy_check_digit.new(#cert_id)
checking_policy_number.create_check_digit
end
end
run = Run_number_check_interface.new
run.run
modulo_7.rb
This program removes the first digit (index 0) of a 7 digit number and returns the difference 7%18 is 4 since 4 is remainder of how many times 7 can fit into 18.
class Get_policy_check_digit
def initialize(cert_id)
#instance variable
#cert = cert_id
end
def create_check_digit
cert_id_6 = #cert.to_s
cert_id_6.slice!(0)
puts cert_id_6
check_digit = cert_id_6.to_i % 7
puts "Your check digit is #{check_digit}"
end
end
# n = Get_policy_check_digit.new(1121546) When uncommented this will create a new instance
# of Get_policy_check_digit with the parameter 1121546
# n.create_check_digit This will run the method create_check_digit with the
# parameter 1121546
Instance variables are scoped to an individual instance of a class. So when you say #cert_id = Integer(gets) inside Number_check_interface, you are only setting #cert_id for that particular instance of Number_check_interface. Then, when you later write Get_policy_check_digit.new(#cert_id) inside Run_number_check_interface, you are referring to an entirely different #cert_id, one which is specific to that particular instance of Run_number_check_interface, and not to the Number_check_interface you stored in n earlier.
The simple solution is to return #cert_id from Number_check_interface#get_cert_number, and then pass the returned value to Get_policy_check_digit.new:
class Number_check_interface
def get_cert_number
print "You are about to check receive the check number for a policy/cert id."
#cert_id = nil # This is an instance variable. It's only accessible
# from inside this instance of `Number_check_interface`
until #cert_id.is_a?(Fixnum) do
puts " Enter the policy/cert ID. "
begin
#cert_id = Integer(gets)
rescue ArgumentError
end
end
return #cert_id # Return the contents of #cert_id
end
end
class Run_number_check_interface
def run
load 'modulo_7.rb'
n = Number_check_interface.new
cert_number = n.get_cert_number # Here we call `get_cert_number` and
# set `cert_number` to it's return
# value.
# Notice how we use `cert_number` here:
checking_policy_number = Get_policy_check_digit.new(cert_number)
checking_policy_number.create_check_digit
end
end
Other tips:
Convention in Ruby is to name classes with CamelCase.
Require dependencies at the top of your files, not in the middle of method calls.
Unless you have a very good reason not to, use require, not load
You might want to think a bit harder about what purpose these classes serve, and what behavior they are intending to encapsulate. The API seems a bit awkward to me right now. Remember, tell, don't ask.
Why are these separate classes? The design here seems strange, is this ported from another language? It's more complicated than it needs to be. Without changing your structure, here's what's wrong:
In Run_number_check_interface you are reading #cert_id, it doesn't have an instance variable named that, but Number_check_interface does. Just return it from get_cert_number:
class Number_check_interface
def get_cert_number
print "You are about to check receive the check number for a policy/cert id."
cert_id = nil
until cert_id.is_a?(Fixnum) do
puts " Enter the policy/cert ID. "
begin
cert_id = Integer(gets)
rescue ArgumentError
end
end
cert_id # <-- returing the value here
end
end
class Run_number_check_interface
def run
load 'modulo_7.rb'
n = Number_check_interface.new
cert_id = n.get_cert_number # <-- saving here
checking_policy_number = Get_policy_check_digit.new(cert_id) # <-- no longer an ivar
checking_policy_number.create_check_digit
end
end
run = Run_number_check_interface.new
run.run
This piece of code is supposed to loop through an array of IP addresses and checks to see if a port is open.
class Ranger
def initialize(port,file)
#port = port
#file = file
#arr = []
end
def regex(f)
reg = IO.read(f)
reg.scan /(?:\d{1,3}\.){3}\d{1,3}/
end
def fileread
if File.exists?(#file)
#arr << regex(#file).to_s
begin
#arr.each do |ip|
sock = Socket.new(:INET, :STREAM)
sockaddr = Socket.sockaddr_in(#port, ip.to_i)
puts "Host: #{ip}:#{#port} Open" if sock.connect(sockaddr)
next
end
rescue Errno::ECONNREFUSED
false
end
end
end
end
The code seems to almost completely work, except for one thing. It prints out the success text i.e "Host: #{ip}:#{#port} Open". The problem is that it prints out the entire array where #{ip} is, like this: ["xx.xx.xx.xx","xx.xx.xx.xx","xx.xx.xx.xx"]:22 Open.
It seems to have something to do with the .to_s and .to_i in the script, but it won't work at all without those.
From what I can see you are only adding ONE thing to the #arr variable...
#arr << regex(#file).to_s
regex() calls string.scan () which returns an array (presumably your 3 IPs
you're then converting the array to a string and appending the string to #arr.
either you want
#arr = regex(#file) # replace
or
#arr += regex(#file) # concatenate
When do I know when to declare a variable and not to in Ruby?
I would like to know why the first code needs input to be declared as a string and outside of the block, while the second block doesn't.
input = ''
while input != 'bye'
puts input
input = gets.chomp
end
puts 'Come again soon!'
versus:
while true
input = gets.chomp
puts input
if input == 'bye'
break
end
end
puts 'Come again soon!'
No variable is ever declared in Ruby. Rather, the rule is that a variable must appear in an assignment before it is used.
Look at the first two lines in your first example:
input = ''
while input != 'bye'
The while condition uses the variable input. Therefore the assignment is necessary before it. In the second example:
while true
input = gets.chomp
puts input
Again, the variable input is assigned before it is used in the puts call. All is right with the world in both examples.
I am attempting to learn Ruby by converting a Java program to Ruby, but I've been coming up with an error surrounding this block of code:
def create
#user_input = String.new()
# #word_arr = Array.new
print "Enter the text to be converted to pig latin, EOF to quit: "
while gets do
STDOUT.flush
#user_input = gets.chomp
#word_arr = #user_input.string.split(' ')
#word_arr.each { |x| puts x.engToLatin() + ' '}
print "EOF to Quit"
#user_input = ""
end
end
I've been getting this error:
EnglishToPigLatin.rb:14:in `create': private method `chomp' called for nil:NilClass (NoMethodError)
from EnglishToPigLatin.rb:60
This is the area around line 60:
#if __FILE__ == $0
mg = EnglishToPigLatin.new
mg.create
#end
Essentially what I am trying to do is while there is still input, get that input, split it up into individual words, and run each word through a Pig Latin conversion method.
It looks like you're trying to get input inside of your loop.
Try
loop do
user_input = gets.chomp!
word_arr = user_input.to_s.split(' ')
word_arr.each { |x| puts x.engToLatin() + ' '}
puts "EOF to Quit"
end
Otherwise you're trying to get the next line of input when there isn't one. Additionally, do isn't necessary for a while statement.
You also don't need to reset #user_input to ''.
And since this is all in a block, you don't need to use instance variables, unless the methods you call need them.
Also your conditional is always true. gets will block until it gets a line of input. You can use loop for an infinite loop that ends on an interrupt.
Also, you needn't flush STDOUT if you use a puts for the last line there instead of a print.
The whole thing could be a script or a method in a module. An instance doesn't even need to be made. And if you do, instead of using two lines with your mg.create, you should define an initialize method. This is used as a constructor then, and whatever you set when you create an instance should be put there.
It can all be done like this:
loop do
puts gets.chomp.split(' ').map{ |x| x.engToLatin() }.join(' ')
puts "EOF to Quit"
end
Mario's answer is right. But I have the following notes.
You can still use the while construction as below.
+' ' implies that you don't want line breaks after each word. I changed that part. map and join is common in similar cases. print does not add a line break while puts does.
I am not sure what you are trying to do with STDOUT.flush. If you wanted to scroll to the top of the screen before each output, use system('clear').
You have a method entToLatin, and it should work, but it is a ruby convention to use underscore, like eng_to_latin for methods (although there are a few exceptions).
So a more rubyish way would be:
def create
print "Enter the text to be converted to pig latin, EOF to quit: "
while input = gets.strip and input != 'EOF'
system('clear')
puts input.split(/\s+/).map{|x| x.engToLatin}.join(' ')
puts "EOP to Quit"
end
end
And if you are using ruby 1.9.2, you can shorten map so that:
def create
print "Enter the text to be converted to pig latin, EOF to quit: "
while input = gets.strip and input != 'EOF'
system('clear')
puts input.split(/\s+/).map(:engToLatin).join(' ')
puts "EOP to Quit"
end
end