cannot load such file -- write_file

Question

I'm new to Ruby. I just started so it's strange to me because I am coming from a Java & C# background.

write_file.rb contains:

class Write_file

  def write_method(title, text)

    @title = title+".txt"
    my_file = File.new(@title, 'w')
    #my_file.close
    puts "Creating file..."

    @text = text
    my_file = File.open(@title, 'w'){|file|
      file.puts @text
    }
    puts "done!"
  end
end

read_file.rb contains:

class Read_file
  def read_method(title)
    file = title + ".txt"
    File.readlines(file).each do |line|
      puts line
    end
  end
end

write_read.rb contains:

require "write_file"
require "read_file"
puts "Choose what you want to do :\n1. Write a file\n2. Read a file"
input = gets.to_i
if input.equals? 1
  puts "Enter name of file here:"
  title = gets.chomp
  puts "Enter text here:"
  text =gets.chomp
  x = Write_file.new
  x.write_method(title,text)
  puts x
elsif input.equals? 2
  puts "Enter name of file to read"
  file = gets.chomp
  rid = Read_file.new
  rid.read_method(file)
  puts rid
else puts "Invalid selection"
end

But I get the following error:

/usr/local/rvm/rubies/ruby-2.2.1/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- write_file (LoadError)                                            
    from /usr/local/rvm/rubies/ruby-2.2.1/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'                                                                                
    from /home/ubuntu/workspace/ruby/write_read.rb:1:in `<main>'

Use [`require_relative`](http://stackoverflow.com/questions/3672586/what-is-the-difference-between-require-relative-and-require-in-ruby). — ndnenkov, Sep 05 '15 at 19:06
Welcome to Stack Overflow. Please take more time when creating your question, and review it when done. Your code examples aren't formatted well, and make it more difficult to read, which affects our ability to help you. — the Tin Man, Sep 05 '15 at 19:27
ndn thanks man. But I usually saw require used in most online examples and books — connelblaze, Sep 05 '15 at 19:33
You can't trust "online". WHEN were they written? The internet never forgets and is chock-full of out of date information. Ruby is a moving target and the documents don't get updated to reflect the changes usually. http://ruby-doc.org/ is your go-to for accurate information about the language's methods and classes. `require_relative` is the standard method used now to load files you've written that are part of your code hierarchy. — the Tin Man, Sep 05 '15 at 19:53

score 1 · Answer 1 · answered Sep 05 '15 at 19:34

When you run a script from the command line, you'll typically us a command like: ruby my_script.rb. When you do that you are running that script in the context of the ruby executable, and any paths need to be accessible to the the ruby executable. Gems etc. are registered with the executable, so their paths can be accessed reasonably easily. But other scripts that you write won't be known to the ruby executable, and therefore won't be accessible via a simple require <filename>.

So to get around this you can do a couple of thing. One is to do this:

require File.expand_path('write_file', File.dirname(__FILE__))

That tells ruby that the file's location is relative to the script file being run.

However, since ruby 1.9.3 there is a simpler solution; use require_relative. This is the equivalent to the expand_path code above:

require_relative 'write_file'

the Tin Man · Answer 2 · 2015-09-05T19:54:21.507

There are several things you're not doing correctly.

Your error is a result of not understanding how Ruby can load files to be included into your script.

require, by default, will load files from Ruby's core and standard libraries and any gems you've installed. It can also use absolute and relative paths. Sometimes people will push local directories into the search path to make it possible for require to find local files, but that's not necessary or particularly recommended; The reasons why involve security for your script and led to the creation of require_relative.

require_relative, by default, will load files from the current directory, or other directories if you've specified a relative path to the file. In your code you should use require_relative to load write_file.

Moving on:

Write_file and Read_file are not good names for classes. We use CamelCase for class names, so WriteFile or ReadFile would be more appropriate, but classes are things, not actions, so File would be appropriate (if it wasn't already taken by the built-in File class) and inside the class would be write and read methods (which again already exist in the built-in File class).
Your use of instance variables like @title isn't correct. Consider an instance variable to be a global variable accessible by an instance of the class only inside its instance. You're using @title only within a given method, not outside of it, so a local variable title would be appropriate. Variable scope, their visibility within blocks, classes, methods, etc., is confusing at first so spend time up front getting a good handle on them or you'll be spewing variables all over and running into problems with them being stomped on.

the Tin Man; I think you're a faculty or lecturer or program for a living. Points taken sir! — connelblaze, Sep 05 '15 at 20:27

cannot load such file -- write_file

2 Answers2