How do I use Thor actions without requiring a Thor CLI app?

Question

There are some great helper methods from Thor::Actions (http://textmate.rubyforge.org/thor/Thor/Actions.html) that I want access to but I cannot seem to use them without employing a Thor CLI app.

I've tried simply:

require "rubygems"
require "thor"

Thor::Actions.create_file "foo.txt", "contents"

Which throws:

run.rb:4:in '<main>': undefined method 'create_file' for Thor::Actions:Module (NoMethodError)

I realize I might be missing something really simple here. Thanks.

Answer 1

Thor intends for your classes to subclass the Thor class. The Thor class then includes and extends modules allowing their methods to be class methods. If you look at the source, for example Actions.rb, you will see what I mean:

# thor/lib/thor/actions.rb

class Thor
  module Actions

    # this is the interesting part and answers your question
    def self.included(base) #:nodoc:
      base.extend ClassMethods
    end

    module ClassMethods

This is a common Ruby idiom that uses a mixin to define class methods (as opposed to instance methods) on its inclusor.

As an example,

[2] pry(main)> class Klass
[2] pry(main)*   module Mod  
[2] pry(main)*     def self.included(base)    
[2] pry(main)*       base.extend ClassMethods      
[2] pry(main)*     end  
[2] pry(main)*     module ClassMethods    
[2] pry(main)*       def act_as_class_method      
[2] pry(main)*         puts "Im a class method now!!!"        
[2] pry(main)*       end  
[2] pry(main)*     end  
[2] pry(main)*   end  
[2] pry(main)* end  
=> nil

Now calling

Klass::Mod.act_as_class_method

results in the same error you had

NoMethodError: undefined method `act_as_class_method' for Klass::Mod:Module
from (pry):26:in `__pry__'

But if you subclass Klass and include Klass::Mod the included call back extends the ClassMethod module, letting you use the methods defined in ClassMethods as class methods

[4] pry(main)> class Example < Klass
[4] pry(main)*   include Klass::Mod

[4] pry(main)*   self.act_as_class_method
[4] pry(main)* end  

=> Im a class method now!!!
=> nil

This took me a while to figure out at first, so don't feel bad and no, its not that simple or obvious.

Answer 2

To use Thor::Actions without inheriting from Thor:

class Builder # or whatever
  # To get your hands on the `from_superclass` method
  include Thor::Base

  # What we're interested in…
  include Thor::Actions
  source_root "/path/to/where/things/come/out"

  def initialize(*)
    # whatever you might want to do
    @destination_stack = [self.class.source_root]
  end
end

Hope someone else finds this useful. Tried and tested with Thor v0.18.1; as this is internal API stuff it's likely to break at some point in the future.

You can then use the helper methods in your Builder class like so:

class Builder
  def build
    in_root { 'do things' }
    create_file 'etc'
  end
end

Edit: If you want to control where you create files and folders you need to set destination_root like so:

class Builder
  include Thor::Base
  include Thor::Actions
  source_root Dir.pwd

  def initialize(root)
    self.destination_root = File.expand_path(root)
  end

  def build
    directory 'templates', 'target'
  end
end