Thor
Description
Thor is a simple and efficient tool for building self-documenting command line utilities. It removes the pain of parsing command line options, writing “USAGE:” banners, and can also be used as an alternative to the Rake build tool. The syntax is Rake-like, so it should be familiar to most Rake users.
Installation
$ gem install thor
or
$ gem install wycats-thor -s http://gems.github.com
Usage
Map options to a class. Simply create a class with the appropriate annotations
and have options automatically map to functions and parameters.
Example:
class App < Thor # [1]
map “-L” => :list # [2]
desc “install APP_NAME”, “install one of the available apps” # [3]
method_options :force => :boolean, :alias => :string # [4]
def install(name)
user_alias = options[:alias]
if options.force?
# do something
end
# other code
end
desc “list [SEARCH]”, “list all of the available apps, limited by SEARCH”
def list(search=“”)
# list everything
end
end
Thor automatically maps commands as such:
thor app:install myname –force
That gets converted to:
App.new.install(“myname”)
# with {‘force’ => true} as options hash
- Inherit from Thor to turn a class into an option mapper.
- Map additional non-valid identifiers to specific methods. In this case, convert -L to :list
- Describe the method immediately below. The first parameter is the usage information, and the second parameter is the description.
- Provide any additional options that will be available the instance method options.
Types for method_options
- :boolean - is parsed as –option or –option=true
- :string - is parsed as –option=VALUE
- :numeric - is parsed as –option=N
- :array - is parsed as –option=one two three
- :hash - is parsed as –option=name:string age:integer
Besides, method_option allows a default value to be given. Examples:
method_options :force => false
#=> Creates a boolean option with default value false
method_options :alias => “bar”
#=> Creates a string option with default value “bar”
method_options :threshold => 3.0
#=> Creates a numeric option with default value 3.0
You can also supply :option => :required to mark an option as required. The
type is assumed to be string. If you want a required hash with default values
as option, you can use method_option which uses a more declarative style:
method_option :attributes, :type => :hash, :default => {}, :required => true
All arguments can be set to nil (except required arguments), by suppling a no or
skip variant. For example:
thor app name –no-attributes
In previous versions, aliases for options were created automatically, but now
they should be explicit. You can supply aliases in both short and declarative
styles:
method_options %w( force -f ) => :boolean
Or:
method_option :force, :type => :boolean, :aliases => “-f”
You can supply as many aliases as you want.
NOTE: Type :optional available in Thor 0.9.0 was deprecated. Use :string or :boolean instead.
Namespaces
By default, your Thor tasks are invoked using Ruby namespace. In the example
above, tasks are invoked as:
thor app:install name –force
However, you could namespace your class as:
module Sinatra
class App < Thor
# tasks
end
end
And then you should invoke your tasks as:
thor sinatra:app:install name –force
If desired, you can change the namespace:
module Sinatra
class App < Thor
namespace :myapp
# tasks
end
end
And then your tasks should be invoked as:
thor myapp:install name –force
Invocations
Thor comes with a invocation-dependency system as well, which allows a task to be invoked only once. For example:
class Counter < Thor
desc “one”, “Prints 1, 2, 3”
def one
puts 1
invoke :two
invoke :three
end
desc “two”, “Prints 2, 3”
def two
puts 2
invoke :three
end
desc “three”, “Prints 3”
def three
puts 3
end
end
When invoking the task one:
thor counter:one
The output is “1 2 3”, which means that the three task was invoked only once.
You can even invoke tasks from another class, so be sure to check the
documentation.
Notice invocations do not share the same object. I.e, Thor will instantiate Counter once to invoke the task one, then, it instantiates another to invoke the task two and another for task three. This happens to allow options and arguments to parsed again. For example, if two and three have different options and both of them were given to the command line, calling invoke makes them be parsed each time and used accordingly by each task.
Thor::Group
Thor has a special class called Thor::Group. The main difference to Thor class
is that it invokes all tasks at once. The example above could be rewritten in
Thor::Group as this:
class Counter < Thor::Group
desc “Prints 1, 2, 3”
def one
puts 1
end
def two
puts 2
end
def three
puts 3
end
end
When invoked:
thor counter
It prints “1 2 3” as well. Notice you should describe (using the method desc)
only the class and not each task anymore. Thor::Group is a great tool to create
generators, since you can define several steps which are invoked in the order they
are defined (Thor::Group is the tool use in generators in Rails 3.0).
Besides, Thor::Group can parse arguments and options as Thor tasks:
class Counter < Thor::Group
# number will be available as attr_accessor
argument :number, :type => :numeric, :desc => “The number to start counting”
desc “Prints the ‘number’ given upto ‘number+2’”
def one
puts number + 0
end
def two
puts number + 1
end
def three
puts number + 2
end
end
The counter above expects one parameter and has the folling outputs:
thor counter 5
# Prints “5 6 7”
thor counter 11
# Prints “11 12 13”
You can also give options to Thor::Group, but instead of using method_option
and method_options, you should use class_option and class_options.
Both argument and class_options methods are available to Thor class as well.
Actions
Thor comes with several actions which helps with script and generator tasks. You
might be familiar with them since some came from Rails Templates. They are:
say, ask, yes?, no?, add_file,
remove_file, copy_file, template, directory,
inside, run, inject_into_file and a couple more.
To use them, you just need to include Thor::Actions in your Thor classes:
class App < Thor
include Thor::Actions
# tasks
end
Some actions like copy file requires that a class method called source_root is
defined in your class. This is the directory where your templates should be
placed. Be sure to check the documentation on actions.
Generators
A great use for Thor is creating custom generators. Combining Thor::Group,
Thor::Actions and ERB templates makes this very easy. Here is an example:
class Newgem < Thor::Group
include Thor::Actions
# Define arguments and options
argument :name
class_option :test_framework, :default => :test_unit
def self.source_root
File.dirname(FILE)
end
def create_lib_file
template(‘templates/newgem.tt’, “#{name}/lib/#{name}.rb”)
end
def create_test_file
test = options[:test_framework] == “rspec” ? :spec : :test
create_file “#{name}/#{test}/#{name}_#{test}.rb”
end
def copy_licence
if yes?(“Use MIT license?”)
# Make a copy of the MITLICENSE file at the source root
copy_file “MITLICENSE”, “#{name}/MITLICENSE”
else
say “Shame on you…”, :red
end
end
end
Doing a thor -T will show how to run our generator. It should read:
thor newgem NAME. This shows that we have to supply a NAME
argument for our generator to run.
The create_lib_file uses an ERB template. This is what it looks like:
class <%= name.capitalize %>
end
The arguments that you set in your generator will automatically be passed in
when template gets called. Be sure to read the documentation for
more options.
Running the generator with thor newgem devise will
create two files: “devise/lib/devise.rb”, and “devise/test/devise_test.rb”. The user will then be asked (via a prompt by the yes? method) whether or not they would like to copy the MIT License. If you want to change the test framework, you can add the option: thor newgem devise –test-framework=rspec
This will generate two files - “devise/lib/devise.rb” and “devise/spec/devise_spec.rb”.
Further Reading
Thor offers many scripting possibilities beyond these examples. Be sure to read
through the documentation and specs to get a better understanding of the options available.
License
Released under the MIT License. See the LICENSE file for further details.