CODEWITHSUNDEEP
ruby
Friso
Friso

Reputation: 2428

How do I import ruby classes into the main file?

I'm trying to learn how to program with Ruby and I want to create separate files for separate classes, but when I do I get the following message:

NameError: uninitialized constant Book
const_missing at org/jruby/RubyModule.java:2677

(root) at /Users/Friso/Documents/Projects/RubyApplication1/lib/main.rb:1

However, it works if I put the class directly into the main file. How can I solve this?

Main code:

book1 = Book.new("1234", "Hello", "Ruby")
book2 = Book.new("4321", "World", "Rails")

book1.to_string
book2.to_string

Class code:

class Book
  def initialize(isbn,title,author)
    @book_isbn=isbn
    @book_title=title
    @book_author=author
  end
  
  def to_string
    puts "Title: #@book_title"
    puts "Author: #@book_author"
    puts "ISBN: #@book_isbn"
  end
end

Upvotes: 21

Views: 46664

Answers (2)

13aal
13aal

Reputation: 1674

In order to include classes, modules, etc into other files you have to use require_relative or require (require_relative is more Rubyish.) For example this module:

module Format

  def green(input)
    puts"\e[32m#{input}[0m\e"
  end
end

Now I have this file:

require_relative "format" # <= require the file

include Format # <= include the module

def example
  green("this will be green") # <= call the formatting 
end

The same concept goes for classes:

class Example

  attr_accessor :input

  def initialize(input)
    @input = input
  end

  def prompt
    print "#{@input}: "
    gets.chomp
  end
end

example = Example.new(ARGV[0])

And now I have the main file:

require_relative "class_example"

example.prompt

In order to call any class, or module from another file, you have to require it.

I hope this helps, and answers your question.

Upvotes: 30

Keith Bennett
Keith Bennett

Reputation: 4970

You need to instruct the Ruby runtime to load the file that contains your Book class. You can do this with require or require_relative.

The latter is better in this case, because it loads the file relative to the directory in which the file containing the require is specified. Since that's probably the same directory, you can just require_relative the file name, without the .rb extension by convention.

You can google 'require vs require_relative ruby' to find out more about the differences.

Upvotes: 12

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