I am attempting to use the String from a variable to call a Method within the program.
How can one use the String from the Variable to call said Method without having to nest or make multiple checks?
module Player
##location = "location"
def Player.input(input)
if input == "look"
"Call Method from ##location"
end
end
def Player.set_location(input)
##location = input
end
end
def input
print "> "
Player.input(#stdin.gets.chomp)
end
def "name of Method can be same as ##location"
...
end
def "another name of Method can be same as ##location"
...
end
def "another name, etc"
...
end
What do you mean by without having to nest ? I wonder if your code is a contrived example. Defining methods in the special object main is OK for a quick test, if they are also called from main, otherwise they must be put in a class.
So the answer could be as simple as that :
module Player
#location = 'location'
def Player.input(input)
puts "in Player.input(#{input})"
if input == 'look'
puts "Calling method <#{#location}>"
Switch.send(#location)
else
puts 'wrong input, must be "look"'
end
end
def Player.set_location(input)
#location = input
end
end
def input
print "> "
Player.input(gets.chomp)
end
class Switch
def self.abc
puts 'in abc'
end
def self.def
puts 'in def'
end
def self.location
puts 'in location'
end
def self.method_missing(name, *args, &block)
puts "There is no method #{name} in #{self.name}"
end
end
input
input
Player.set_location('abc')
input
Player.set_location('xyz')
input
Execution :
$ ruby -w t.rb
> looc
in Player.input(looc)
wrong input, must be "look"
> look
in Player.input(look)
Calling method <location>
in location
> look
in Player.input(look)
Calling method <abc>
in abc
> look
in Player.input(look)
Calling method <xyz>
There is no method xyz in Switch
Related
Undefined method for nil:Nilclass
In a class, a method counts the number of words in a paragraph.An error occurs when a method is called(1). I can’t understand how to pass the argument methods using send.
If I remove the class and put the def calc_1(paragraph) method into the loop, then everything works, I start calling the select method. It turns out he does not see my books variable with text, when there is a class.
#books = "You can use this knowledge to create small tools that might help."
class Filecalculation
def select
loop do
puts "# Will we search : сounting words in text File(1)".cyan
print "\n>>>>>> "
input = gets.chomp
search_method = "calc_#{input}".to_sym
if (respond_to?(search_method))
contents = send(search_method, #books)
end
end
end
def calc_1 paragraph
word_count = paragraph.split.length
puts "#{word_count} words"
end
end
Filecalculation.new.select
If replaced by search_method = "calc_#{input}".to_sym also works.
Helped add def initialize #books end.
Instead of contents = send (search_method, #books) you can use send (search_method, #books).
require "colorize"
class Filecalculation
def initialize
#books = "You can use this knowledge to create small tools that might help you."
end
def calc_1 paragraph
word_count = paragraph.strip.squeeze(' ').count(' ') + 1
puts "#{word_count} words"
end
def select
loop do
puts "# Will we search : Calculation_lines paragraph(1)".cyan
print "\n>>>>>> ".yellow
input = gets.chomp
search_method = "calc_#{input}" #.to_sym
if (respond_to?(search_method))
contents = send(search_method, #books)
else
puts "exit "
exit
end
end
end
end
Filecalculation.new.select
I've read my code up and down for about 30 mins now. I can't for the life of me see where user_response is undefined. I'm very new to coding so I don't know how much of the code would be appropriate to paste in here. I figure that launch and get_action are essential but the rest couldn't hurt?
error => rb:32:in `launch!': undefined local variable or method `user_response' for
<Guide:0x007fb019984718> (NameError)
class Guide
class Config
##actions = ['list', 'find', 'add', 'quit']
def self.actions
##actions
end
end
def initialize(path=nil)
# locate the restaurant text file at path
Restaurant.filepath = path
if Restaurant.file_usable?
puts "Found restaurant file."
# or IF a new text file can't be created, create a new file
elsif Restaurant.create_file
puts "Created restaurant file."
# exit if create fails
else
puts "Exiting"
exit!
end
end
def launch! #! means that it is a strong powerful method!
introduction
# action loop
result = nil
until result == :quit
action = get_action
result = do_action(user_response)
end
conclusion
end
def get_action
action = nil
# Keep asking for user input until we get a valid action
until Guide::Config.actions.include?(action)
puts "Actions: " + Guide::Config.actions.join(", ") if action
print "> "
user_response = gets.chomp
action = user_response.downcase.strip
end
return action
end
def do_action(action)
case action
when 'list'
puts "Listing..."
when 'find'
puts "Finding..."
when 'add'
puts "Adding..."
when 'quit'
return :quit
else puts " I don't understand that command."
end
end
def introduction
puts "<<< Welcome to the Food Finder >>>"
puts "This is an interactive guide to help you find the food you crave."
end
def conclusion
puts "<<< Goodbye and Bon Appetit! >>>>"
end
end
I think you want to do this :
def launch! #! means that it is a strong powerful method!
introduction
# action loop
result = nil
until result == :quit
result = do_action(get_action)
end
conclusion
end
The only time you define a variable called user_response is in your get_action method.
The way you define it there makes it a local variable and it will not be accessible from anywhere but inside the get_action method.
Assuming I have the following proc:
a = Proc.new do
puts "start"
yield
puts "end"
end
Also assuming I pass a to another method which subsequently calls instance_eval on another class with that block, how can I now pass a block onto the end of that method which gets yielded in a.
For example:
def do_something(a,&b)
AnotherClass.instance_eval(&a) # how can I pass b to a here?
end
a = Proc.new do
puts "start"
yield
puts "end"
end
do_something(a) do
puts "this block is b!"
end
Output should of course should be:
start
this block is b!
end
How can I pass the secondary block to a in the instance_eval?
I need something like this for the basis of a Ruby templating system I'm working on.
You can't use yield in a. Rather, you have to pass a Proc object. This would be the new code:
def do_something(a,&b)
AnotherClass.instance_exec(b, &a)
end
a = Proc.new do |b|
puts "start"
b.call
puts "end"
end
do_something(a) do
puts "this block is b!"
end
yield is only for methods. In this new code, I used instance_exec (new in Ruby 1.9) which allows you to pass parameters to the block. Because of that, we can pass the Proc object b as a parameter to a, which can call it with Proc#call().
a=Proc.new do |b|
puts "start"
b.call
puts "end"
end
def do_something(a,&b)
AnotherClass.instance_eval { a.call(b) }
end
I'm not sure that's the right title for this question, but I don't know how else to ask it. I have classes that need to be registered globally so they can be called later. I have most of it working except for a very important part. When the child inherits from the parent class, it registers a new instance, but when the on_message class method is called, I can't figure out how to set the instance variables that I need.
class MyExtension < ExtensionBase
on_message '/join (.+)' do |username|
# this will be a callback function used later
end
end
class ExtensionBase
def self.inherited(child)
MainAppModule.registered_extensions << child.new
end
def self.on_message(string, &block)
# these need to be set on child instance
#regex = Regexp.new(string)
#on_message_callback = block
end
def exec(message)
args = #regex.match(message).captures
#on_message_callback.call(args)
end
end
# somewhere else in the code, I find the class that I need...
MainAppModule.registered_extensions.each do |child|
puts child.regex.inspect # this is nil and I dont want it to be
if message =~ child.regex
return child.exec(message)
end
end
How can I design this so that the #regex will be set so I can access it within the loop?
I finally found a solution that works, and I have added now the whole code that is executable. Just store the code e.g. in file callexample.rb and call it by ruby callexample.rb
The main difference of my solution to the question is that the call to on_message now creates the instance with the relevant arguments and registers the created instance. Therefore I have deleted the method inherited because I don't need it any more.
I have added some puts statements to demonstrate in which order the code works.
class MainAppModule ## Added class
##registered_extensions = []
def self.registered_extensions; ##registered_extensions; end
end
class ExtensionBase
attr_reader :regex
def self.on_message(string, &block)
MainAppModule.registered_extensions << self.new(string, block)
end
def initialize(string, block)
#regex = Regexp.new(string)
#on_message_callback = block
end
def exec(message)
args = #regex.match(message).captures
#on_message_callback.call(args)
end
end
class MyExtension < ExtensionBase
on_message '/join (.+)' do |username|
# this will be a callback function used later
puts "Callback of #{self} called."
"returnvalue"
end
end
# somewhere else in the code, I find the class that I need...
MainAppModule.registered_extensions.each do |child|
puts "Value of regex: #{child.regex}" # this is no more nil
message = '/join something'
if message =~ child.regex
puts "On match evalue 'child.exec(message)' to: #{child.exec(message)}"
end
end
How do I check if a method is defined on some class directly, not by inheritance or by inclusion/extension? I want something like 'foo?' in the following:
class A
def a; end
end
module B
def b; end
end
class C < A
include B
def c; end
end
C.foo?(:a) #=> false
C.foo?(:b) #=> false
C.foo?(:c) #=> true
Use this:
C.instance_methods(false).include?(:a)
C.instance_methods(false).include?(:b)
C.instance_methods(false).include?(:c)
The method instance_methods return an Array of methods that an instance of this class would have. Passing false as first parameter returns only methods of this class, not methods of super classes.
So C.instance_methods(false) returns the list of methods defined by C.
Then you just have to check if that method is in the returned Array (this is what the include? calls do).
See docs
For objects you can use Object.respond_to?.
Returns true if obj responds to the given method.
For classes take a look at Module.instance_methods
Returns an array containing the names of the public and protected instance methods in the receiver.
Not exactly an answer to the question, but if you're reading this question, you might be interested in this, which uses .instance_methods(false)
class Object
# This is more or less how Ruby does method lookup internally
def who_responds_to?(method, klass_ancestors = nil)
if klass_ancestors.nil?
return who_responds_to?(method, self.class.ancestors)
end
if klass_ancestors.empty?
return nil
end
if klass_ancestors[0].instance_methods(false).include?(method)
return klass_ancestors[0]
end
klass_ancestors.shift
who_responds_to?(method, klass_ancestors)
end
end
For example
class Person
end
module Drummer
def drum
end
end
module Snowboarder
def jump
end
end
module Engineer
def code
end
end
class Bob < Person
include Drummer
include Snowboarder
include Engineer
def name
end
end
puts "who responds to name"
puts bob.who_responds_to?(:name)
puts "\n"
puts "who responds to code"
puts bob.who_responds_to?(:code)
puts "\n"
puts "who responds to jump"
puts bob.who_responds_to?(:jump)
puts "\n"
puts "who responds to drum"
puts bob.who_responds_to?(:drum)
puts "\n"
puts "who responds to dance"
puts bob.who_responds_to?(:dance)
yields
who responds to name
Bob
who responds to code
Engineer
who responds to jump
Snowboarder
who responds to drum
Drummer
who responds to dance
[this line intentionally blank because return value is nil]