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What I do need:
I pass a string that has to set an unmutable object inside an array, but I do not know hot how to make the transition from the string that the user inputs to the object name I need.
What I am intending to do:
I am working on a conversational adventure. The key point is to have a function that creates a command prompt so the user can interact with the game. Whenever the user says "go to somewhere", there is another function called "goto" that compares whether the input is included in the exits of the place where the player is; if so, the attribute "place" for the player takes a new place.
What I did:
I made a command prompt that actually works*
loop do
print "\n >>> "
input = gets.chomp
sentence = input.split
case
when sentence[0] == "inspect"
$action.inspect(sentence[1])
when sentence[0] == "go" && sentence[1] == "to"
$action.goto(sentence[2])
when sentence[0] == "quit"
break
else
puts "\nNo le entiendo Senor..."
end
And I initialized the objects as I need them (the third attribute goes for the exits):
room = Place.new("room", "Room", [newroom], "This is a blank room. You can _inspect_ the -clock- or go to [newroom].", ["this this"])
newroom = Place.new("newroom", "New Room", [room], "This is another blank room. You can _inspect_ the -clock-", ["this this"])
Then I made a method inside the action controller that has to compare and set the places properly. (Beware: monster newbie code following. Protect you eyes).
def goto(destiny) #trying to translate the commands into variable names
if (send "#{destiny}").is_in? $player.place.exits
$player.place = send "#{sentence[2]}"
puts destiny.description
else
puts "I cannot go there."
end
end
I think you want to convert a string to constant. Well it is easy. Read an example:
string = 'Hash'
const = Object.const_get(string) #=> Hash
const.new #=> {}; <- it is an empty Hash!
But be careful. If there's no such a constant you will get uninitialized constant error. In this case your adventures will stop.
I hope I understood your question and you will understand my answer.
How to change string to object, there are few options:
Bad(eval family):
eval("name_of_your_variable = #{21+21}")
eval("puts name_of_your_variable") #42
You can see that eval can make everything. So use with caution.
However, as pointed by #user2422869 you need(be in) scope - place where your variables are saved. So above code won't run everywhere
Everytime you run following method you create another scope
def meth1
puts "defined: #{(defined? local_a) ? 'yes' : 'no'}!"
eval 'local_a = 42'
local_a += 100
eval 'puts local_a'
end
meth1
and here is output:
defined: no!
142
If you want to grab local_a from one of scopes of meth1 you need binding.
def meth2
var_a = 222
binding
end
bin = meth2
bin.eval 'var_a'
#output:
#222
About binding you can read in doc. As for scopes, I don't have good site.
Better:
hash_variable = Hash.new # or just {}
hash[your_string_goes_here] = "some value #{42}"
puts hash[your_string_goes_here]
I don't know if good or bad:
As for this: send "#{destiny}". I assume that your destiny doesn't exist, so you can use method_missing:
def method_missing arg, *args, &block
#do some with "destiny"; save into variable/hash, check if "destiny" is in right place etc.
# return something
end
Related
I want to use an input from gets to access a value in a hash.
This code does not work:
puts "Which word?"
question = gets
question = question.to_s
puts dic_hash["#{question}"]
nor does this:
puts "Which word?"
question = gets
question = question.to_s
puts dic_hash[question]
but this works:
puts "Which word?"
puts dic_hash["zwembad"]
How do I get the gets input from the user to access a value in a hash?
You may not be aware of this, but the gets result includes the return character you typed to submit the value.
result = gets
type "hello"
p result
"hello\n"
Change your gets to gets.chomp to remove the trailing '\n`
puts "Which word?"
question = gets.chomp
puts dic_hash[question]
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Well when Input a number, it doesn't print out any of the strings for the given value. if i put in 100, shouldn't it print "go to server room"?
stress = gets.chomp!
def stress
if stress === 100
p "Go to server room"
elsif stress > 50
puts "Take a break"
else
p "Continue working"
end
end
p stress
if i put in 100, shouldn't it print "go to server room"?
I assume that you want your program to read user input and then print different messages depending on that input.
[I'm] new to Ruby
Okay, so first of all, Ruby doesn't do implicit type conversion like JavaScript or PHP. Or not to the same extent. It does allow you to compare floats and integers:
1.0 == 1 #=> true
but comparing strings and integers doesn't work that way:
'1' == 1 #=> false
You have to convert it yourself:
'1'.to_i == 1 #=> true
Since your input is supposed to be an integer, we can convert it right away:
stress = gets.to_i
When entering 100enter, gets will return "100\n" and to_i will interpret that as an integer, returning 100 (to_i ignores the trailing newline, so we don't need chomp).
stress is now an integer, so you can compare it to other integers:
if stress == 100
puts "Go to server room"
elsif stress > 50
puts "Take a break"
else
puts "Continue working"
end
I've changed === to ==. For comparisons you almost always want the latter. === has special meaning in Ruby. Just avoid it for now.
The above code would already work, but you wanted a method. You could call your method stress, i.e. use the same name for the variable and the method. But it makes your code much harder to understand. So let's choose a different method name, e.g. message. While we're at it, let's also remove the repeated puts calls, so it just returns the message without printing it:
def message(stress)
if stress == 100
"Go to server room"
elsif stress > 50
"Take a break"
else
"Continue working"
end
end
You can call the above method via:
input = gets.to_i
puts message(input) # <- 'puts' is now here
I've deliberately chosen a different variable name for the input to distinguish it from the method argument.
You have a few problems here. For one, as someone already mentioned, you are not passing an argument to your method. For another, the gets method returns a String, not an integer, so if you pass the result in you are comparing a String to an integer.
Rework your method like this:
def stress(level_string)
level = level_string.to_i
if level == 100
"Go to server room"
elsif stress > 50
"Take a break"
else
"Continue working"
end
end
Now you can try:
>> level_string = gets.chomp!
>> 100
#> "100"
>> stress(level_string)
#> "Go to server room"
In your statement
p stress
you output the value of the variable named stress, not the value returned by the method stress.
You can have a method and a variable of the same name, but then you have to invoke the method using parenthesis:
p stress()
In your particular case, you would then run however into the next problem: Inside your method stress, you are in a nested scope, which means that the outside variable stress is not visible. Hence, in the statement
if stress === 100
you refer to the method stress, i.e. you have a recursion.
There are several possible solutions:
Pass the variable by parameter
Change the name of the variable
Change the name of the method
As a rule of thumb, I recommend to
never give a variable and a method the same name, and
do not access variables from outer scope inside a method
unless you have very good reasons to do otherwise.
Your variable and your method definition have the same name. Try changing:
stress = gets.chomp!
to
var = gets.chomp!
Then set up your method to accept the variable:
def stress(s)
if s.to_i == 100
p "Go to server room"
elsif s.to_i > 50
puts "Take a break"
else
p "Continue working"
end
end
p stress(var)
You can also do it close to what you were doing, just use a variable other than the name of your method:
var = gets.chomp!
def stress
if self.to_i == 100
p "Go to server room"
elsif self.to_i > 50
puts "Take a break"
else
p "Continue working"
end
end
p var.stress
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I'm new to ruby, and I'm trying to make a simple calculator in which a user types in a simple problem (such as addition or subtraction) and the answer is returned. The problem is when the user types in a question, the question itself is being returned instead of the answer to that question.
puts "How many Questions?"
questions = gets.chomp.to_i
questions.times do |problem|
puts "question: "
problem = gets.chomp
puts "answer: #{problem}"
end
Inside your loop, instead of:
problem = gets.chomp
puts "answer: #{problem}"
Try this:
problem = gets.chomp
solved_problem = eval(problem)
puts "answer : #{solved_problem}"
eval will take care of interpreting your string as a Ruby instruction. But it's very messy, because anyone could write any Ruby program in your input and eval will make it run, so it's not safe at all.
If you only want to take care of simple operations, you can use a regex first to check if the input string looks like what you want:
problem_is_ok = (problem =~ /^\d+ *[+-] *\d+$/)
This will be true if the string starts with a number, followed by 0 to many spaces, followed by either a + or - sign, followed by 0 or more spaces, followed by another number and nothing else. Then you raise an error if this is not true.
Your loop now look like this:
questions.times do |problem|
puts "question: "
problem = gets.chomp
problem_is_ok = (problem =~ /^\d+ *[+-] *\d+$/)
if problem_is_ok
puts "answer: #{eval(problem)}"
else
#I raise an error, but you might aswell just print it instead for your simple program
raise ArgumentError("Can't compute this")
end
end
Add and subtract can be simple ruby definitions
We pass in 5 and 1
The lower portion of the code is the clear user interface implementation
when we loop we do it 3 times
It outputs 3 options for the user to select from
We read in with chomp, standard in, the keyboard, chooses 1, 2, or 3
If elsif statements conditionally select for each case
Using string interpolation we render the variables a and b into a new string,
and run their respective methods (add or subtract)
Converting that methods integer output to a string, and concatenate it.
Outputting that to the users screen
The 3rd option does no calculation,
instead it prints to users screen a simple string
our else condition catches the case when people don't enter one of the choices of 1, 2 or 3
It tells you to correct your choice to the options provided
Hope this helps
#!/usr/bin/env ruby
questions = 3
a, b = 5, 1
def add(a,b)
a + b
end
def subtract(a,b)
a - b
end
questions.times do |questions|
puts "Please choose:
1. add
2. subtract
3. exit"
questions = gets.chomp
if questions == '1'
puts "#{a} + #{b} = " + add(a,b).to_s
elsif questions == '2'
puts "#{a} - #{b} = " + subtract(a,b).to_s
elsif questions == '3'
puts 'exiting, goodbye.'
exit
else
p 'please choose again'
end
end
I am new to Ruby.
I need to make this script work:
puts "Do you like cats?"
ask = gets
def ask(n)
if ask == yes
return "I do too"
end
if ask == no
return "Dogs are better"
end
end
puts "#{ask(n)}"
Error message is :
pracif.rb:15:in <main>': undefined local variable or methodn' for
main: Object (NameError)
Here's a script that would work for you :
puts "Do you like cats?"
answer = gets
def ask(n)
if n == 'yes'
return "I do too"
end
if n == 'no'
return "Dogs are better"
end
end
puts ask(answer.downcase.chomp)
Explaination
As the error said you were trying to pass in a variable n which was not defined
Secondly you have a method name ask same as variable name. I've renamed the variable to answer instead
Thirdly, enclose yes and no in quotes
And finally, since you are using gets a \n gets appended like yes\n so none of your conditions would match. So i've used chomp to remove \n. And also used downcase to make input case insensitive.
EDIT
As mentioned by #Jordan in the comments, there is no reason to use string interpolation for the puts statement. So it's enough to call the method directly.
There are a bunch of issues with your code. Try something more like:
def reply(response)
return 'I do too' if response == 'yes'
return 'Dogs are better' if response == 'no'
'Invalid response!'
end
puts 'Do you like cats?'
response = gets().chomp()
puts reply(response)
Pay attention to the variable names. If you keep them descriptive, it is easier to spot mistakes.
Your script has no n local variable defined that you are passing to your ask(n) method at the end.
Rename your ask variable that your script gets from user to answer for example and pass it to your ask method at the end like so:
Updated code to fix other problem I did not see in the first run.
puts "Do you like cats?"
answer = gets.chomp
def ask(n)
(n == 'yes') ? "I do too" : "Dogs are better"
end
puts "#{ask(answer)}"
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Hi I`m learning from LRtHW and I got stuck....
I have program like this:
require 'open-uri'
WORD_URL = "http://learncodethehardway.org/words.txt"
WORDS = []
PHRASES = {
"class ### < ###\nend" => "Make a class named ### that is-a ###.",
"class ###\n\tdef initialize(###)\n\tend\nend" => "class ### has-a initialize that takes ### parameters.",
"class ###\n\tdef ***(###)\n\tend\nend" =>"class ### has-a function named *** that takes ### parameters.",
"*** = ###.new()" => "Set *** to an instance of class ###.",
"***.***(###)" => "From *** get the *** function, and call it with parameters ###.",
"***.*** = '***'" => "From *** get the *** attribute and set it to '***'."
}
PHRASE_FIRST = ARGV[0] == "english"
open(WORD_URL) do |f|
f.each_line {|word| WORDS.push(word.chomp)}
end
def craft_names(rand_words, snippet, pattern, caps=false)
names = snippet.scan(pattern).map do
word = rand_words.pop()
caps ? word.capitalize : word
end
return names * 2
end
def craft_params(rand_words,snippet,pattern)
names = (0...snippet.scan(pattern).length).map do
param_count = rand(3) + 1
params = (0...param_count).map {|x| rand_words.pop()}
params.join(', ')
end
return names * 2
end
def convert(snippet, phrase)
rand_words = WORDS.sort_by {rand}
class_names = craft_names(rand_words, snippet, /###/, caps=true)
other_names = craft_names(rand_words, snippet,/\*\*\*/)
param_names = craft_params(rand_words, snippet, /###/)
results = []
for sentence in [snippet, phrase]
#fake class name, also copies sentence
result = sentence.gsub(/###/) {|x| class_names.pop}
#fake other names
result.gsub!(/\*\*\*/) {|x| other_names.pop}
#fake parameter list
result.gsub!(/###/) {|x| param_names.pop}
results.push(result)
end
return results
end
# keep going until they hit CTRL-D
loop do
snippets = PHRASES.keys().sort_by { rand }
for snippet in snippets
phrase = PHRASES[snippet]
question, answer = convert(snippet, phrase)
if PHRASE_FIRST
question, answer = answer, question
end
print question, "\n\n> "
odp = gets.chomp
if odp == "exit"
exit(0)
end
#exit(0) unless STDIN.gets
puts "\nANSWER: %s\n\n" % answer
end
end
I understand most of this code, but I have a problem with:
for sentence in [snippet, phrase]
I know that it is a "for" loop and it creates a "sentence" variable, but how does the loop know that it need to look in a key and value of hash "PHRASES"
And my second "wall" is:
question, answer = convert(snippet, phrase)
It looks like it creates and assigns "question" and "answer variables to the "convert" method with "snippet" and "phrase" parameters... again how does it assigns "question" to a key and answer to a value.
I know that this is probably very simple but as for now it blocks my mind :(
For your first question about the for-loop:
Look at where the for-loop is defined. It's inside the convert() method, right? And the convert() method is passed two arguments: one snippet and one phrase. So the loop isn't "looking" for values in the PHRASES hash, you are the one supplying it. You're using the method's arguments.
For your second question about assignment:
In Ruby we can do something called "destructuring assignment". What this means is that we can assign an array to multiple variables, and each variable will hold one value in the array. That's what's happening in your program. The convert() method returns a two-item array, and you're giving a name (question and answer) to each item in the array.
Here's another example of a destructuring assignment:
a, b, c = [1, 2, 3]
a # => returns 1
b # => returns 2
c # returns 3
Try this out in IRB and see if you get the hang of it. Let me know if I can help clarify anything, or if I misunderstood your question. You should never feel bad about asking "simple" questions!