I'm pretty new to building Ruby gems and am taking a stab at my first one. I'm in the middle of writing a generator for my gem that will generate a migration in my Rails app. I'm looking to simply include the gem in the Rails application, run "rails g mygem:install" to have it create the migrations, then run "rake db:migrate" to finalize everything.
I've found several different ways to accomplish similar tasks, but so far nothing has worked. I cannot seem to get the Rails application to find the generator. The latest guide I've tried is located here: http://www.railsdispatch.com/posts/how-rails-3-enables-more-choices-part-1.
Here is what my current gem structure looks like:
-lib/
-generators/
-templates/
-some_migration.rb
-install_generator.rb
-gemname/
-rails/
-railtie.rb
-engine.rb
-tasks/
-gemname.rake
-gemname.rb
-spec/
-gemname.gemspec
Here is what my install_generator.rb file looks like:
require 'rails'
module Gemname
class InstallGenerator < ::Rails::Generators::Base
include Rails::Generators::Migration
source_root File.expand_path('../templates', __FILE__)
desc "add the migrations"
def self.next_migration_number(path)
unless #prev_migration_nr
#prev_migration_nr = Time.now.utc.strftime("%Y%m%d%H%M%S").to_i
else
#prev_migration_nr += 1
end
#prev_migration_nr.to_s
end
def copy_migrations
migration_template "some_migration.rb", "db/migrate/some_migration.rb"
end
end
end
I'm not sure if there's something I'm missing. I'm testing with a Rails 3.2 application that has my gem listed in its Gemfile and the gem is installed. Is there anything wrong with gem folder structure that might be preventing my generator from showing up? Do I need to require something somewhere?
Any help is appreciated.
Rails no longer automatically loads everything in lib by default, like it used to. For a few methods of requiring your files, check out the answers to this question - Best way to load module/class from lib folder in Rails 3?.
Well, I'm not sure which of the changes I made fixed my problem, but here is what I did:
Changed the name of my generator to gemname_generator.rb and the directory structure of my generator to this:
- lib/
-generators/
-templates/
-gemname_generator.rb
Added this line to my generator:
namespace 'gemname'
I'm now able to run "rails g gemname" in my Rails application and have it call my generator.
Related
I want to share a model between 2 (maybe more in the future) of my rails apps. I couldn't find any clear suggestions, but I picked up some of the questions and answers I've read and came to a conclusion that it has to be done with a "gemmed" plugin engine.
I decide to go with an plugin, because I read that engine is simply a kind of a "full" plugin.
So I created a plugin using: rails plugin new my_models --skip-active-record --skip-test-unit --dummy-path=spec/dummy (the options are for skipping activerecord as an ORM and using rspec for testing).
After I created the plugin, I got the following files:
my_models.gemspec Gemfile Gemfile.lock lib MIT-LICENSE Rakefile README.rdoc spec
I tried to include the model using the following methods:
Just creating an app/models directory and put my model inside
As suggested in this tutorial (and I could see in devise's github), I created a generator in an attempt to generate the model.
Both of them failed, and then I decided to go with the engine suggestion (by just adding --mountable to the options list of the "rails new" command), I got the full rails app structure (with app, bin, db and the rest of the directories), put my model in the app/models dir and it worked like a magic!
As I believe I'm a programmer and not I magician, I don't to do such magics, so can you tell me what's wrong with both of my thin plugin solutions (using generator/creating a model)?? Moreover, what are the advantages of using those generators?
I'm attaching my generator's code, maybe I miss something:
require 'rails/generators/named_base'
require 'mongoid'
module Mongoid
module AttackGenerator
def generate_model
invoke "mongoid:model", [name] unless model_exists? && behavior == :invoke
end
def inject_field_types
inject_into_file model_path, migration_data, after: "include Mongoid::Document\n" if model_exists?
end
def migration_data
field :link_url, type: String
field :token, type: String
end
def model_exists?
File.exists?(File.join(destination_root, model_path))
end
def model_path
#model_path ||= File.join("app", "models", "#{file_path}.rb")
end
end
end
An engine (very good guide) is basically a small Rails app: has controllers, can inject into your rails code in various ways (sharing classes/controllers and such) and most important, can use your main Rails application code transparently.
After thinking a bit about it, I believe you need an engine, the reason is, a simple model still require migrations. Notice that an engine is basically a gem plus some few additions provided by rails.
Although miguiding (plugins in rails are not used anymore), the command rails plugin new blorgh --mountable creates a gem which is a rails engine.
How do you understand if a gem is a rails engine? By the file engine.rb (can be named differently, the contents are the important stuff).
module Blorgh
class Engine < ::Rails::Engine
isolate_namespace Blorgh
end
end
The other important thing you should be aware of, is that rails (actually Bundler.require) auto requires one file for you when you add your custom gem to your gemfile: the file named lib/yourgemname.rb, in this case, lib/blorgh.rb. That's your entry point.
Aside from that, all the other things (gemspec and all the other files) are things created for rubygems. The important part is that you use .gemspec file as your gemfile, just add gems using add_dependency instead of the standard Gemfile syntax. If you want (and you should) learn more about ruby gems, this article is really good
The app directory is autoloaded like rails does, so adding app/models/yourmodel.rb is a good way to have your model autoloaded and shared with all your apps.
The last important thing, are migrations. You have to remember to run your_engine_name:install:migrations in your Rails app to copy your migrations from your engine to your rails app and run them (otherwise you can see the suggestions on this article)
And you are ready. One note! To install your gem you have two options: use your remote git repository (best option) or for local development you can use :path, here two examples that can be added to your Rails apps gemfiles:
# Use this only for development purposes
gem 'yourgem', '1.0.0', path: 'your/local/path/to/gem'
# Use this for deploy and such, you'll need access to that repository
gem 'yourgem', '1.0.0', git: 'yourgiturl'
This should be enough
I have written a generator which creates the following ruby file and folder:
app/tests/test.rb
in the test.rb file I have a Test class which looks like this:
class Test < MyCustomModule::MyCustomClass::Base
...
end
Now, I want to use its functionality in one of the show.html.erb files creating new instance like this:
Test.new(...).render(...).html_safe
but I am getting the following error:
uninitialized constant MyCustomModule::MyCustomClass::Base
I have use the following answer to link my gem and my rails application. It seems to work as I am able to use the generator, but the gem module and class are not seen in the rails application.
Could anyone tell how to fix this issue?
I have try to follow the tips posted here but still nothing changed:
Adding config.autoload_paths += Dir["#{config.root}/lib/**/"] in application.rb file
I have created my gem structure looking at CarrierWave gem, so the naming should be correct
I try to disable config.threadsafe! but it is already disabled since config.cache_classes and config.eager_load are set to false in development
DEPRECATION WARNING: config.threadsafe! is deprecated. Rails
applications behave by default as thread safe in production as long as
config.cache_classes and config.eager_load are set to true.
Also, looking at adding-asset-to-your-gems rails documentation, it is said that:
A good example of this is the jquery-rails gem which comes with Rails
as the standard JavaScript library gem. This gem contains an engine
class which inherits from Rails::Engine. By doing this, Rails is
informed that the directory for this gem may contain assets and the
app/assets, lib/assets and vendor/assets directories of this engine
are added to the search path of Sprockets.
So, I have done this, and put my model class file in assets folder, but the result is the same.
The following screenshots demonstrate my real case:
The screenshot below displays my gem file structure
Here you can see how I am loading the gem in my Rails application Gemfile:
gem 'thumbnail_hover_effect', '0.0.3', github: 'thumbnail_hover_effec/thumbnail_hover_effec', branch: 'master'
Then I am using the gem generator a ruby file with a cutstom name in app/thumbnails/test.rb folder with the following code:
class Test < ThumbnailHoverEffect::Image::Base
...
end
and trying to use the Test class gives me uninitialized constant ThumbnailHoverEffect::Image::Base error.
Back in the gem files, these are how the thumbnail_hover_effect file looks like
require 'thumbnail_hover_effect/version'
require 'thumbnail_hover_effect/engine'
require 'thumbnail_hover_effect/image'
module ThumbnailHoverEffect
# Your code goes here...
end
and hoe the image file looks like:
module ThumbnailHoverEffect
#
class Image
...
end
end
From what you've posted here there is no ThumbnailHoverEffect::Image::Base defined. Rails autoloading conventions (which you should not be depending on a gem btw, more on that later) would be looking for this file in thumbnail_hover_effect/image/base.rb, but the directory structure you printed does not have that. Of course you could define the class in thumbnail_hover_effect/image.rb and it would work, but the abridged snippet you posted does not show that. So where is ThumbnailHoverEffect::Image::Base defined?
If it's in thumbnail_hover_effect/image/base.rb then that would indicate the file is not being loaded. You can sanity check this by putting a puts 'loading this stupid file' at the top of thumbnail_hover_effect/image/base.rb. That will allow you to bisect the problem by seeing whether there is a problem with your definition of the class, or whether the problem is with loading the proper files. Debugging is all about bisecting the problem.
I am using Ruby on Rails 3.2.2. I have implemented a Something plugin (it is almost a gem, but is not a gem) and all related files are in the lib/something directory. Since I would like to automate code generation related to that plugin, I came up with Ruby on Rails Generators. So, for the Something plugin, I am looking for implementing my own generators in the lib/something directory.
How should I make that and what are prescriptions? That is, for example, what rails generate command line should be invoked to properly generate all needed files in the lib/something directory? generators would still work with plugins (not gem)? what are advices about this matter?
I would make it a gem. I've made generators using gems, but I don't know if the generators would still work with plugins.
If you are having difficulty with the command line, I am guessing that you don't need any argument. (If you need an argument, I could copy the provided templates, and if I needed some other argument I'd be lost, so my advise is limited to non-argument.)
I have a generator gem which generates migration files needed for another gem. It checks if the migration with a given root name (w/o the timestamp prefix) is in db/migrate, and otherwise creates it.
Here is my code. I think this example is the help you need.
class ItrcClientFilesGenerator < Rails::Generators::Base
source_root(File.dirname(__FILE__) + "/../src")
desc "Generator to create migrations for needed db tables"
def create_itrc_client_files
prefix = DateTime.now.strftime("%Y%m%d%H%M")
existing_migrations =
Dir.glob("db/migrate/*itrc*").map do |path|
File.basename(path).gsub(/^\d*_/, '')
end
Dir.glob(File.dirname(__FILE__) + "/../src/*").sort.each_with_index do |src_filepath, index|
src_filename = File.basename(src_filepath)
unless existing_migrations.include?(src_filename.gsub(/^\d*_/, '')) then
this_prefix = "#{prefix}#{'%02i' % index}_"
dst_filename = src_filename.gsub(/^\d*_/, this_prefix)
copy_file(src_filename, "db/migrate/" + dst_filename)
end
end
end
end
So there's this great plugin I've gotten used to using in my Rails 2 projects called Bootstrapper. It essentially duplicates the functionality of the seeds.rb file, but I like it because it lets you break up your bootstrap process into concise chunks.
Anyway, I've gone so far as to fork the project and attempt to turn it into a Rails 3 gem. I've been able to get the gem to initialize and register the rake tasks and generators OK. However, I'm running into a problem with the Bootstrapper class itself. It won't load in the Rails project unless it's in a module.
That is, if I place the Bootstrapper class in a file by itself and require that file in my Railtie, then in my Rails app, it can't find the Bootstrapper class. If I put the class in a module and call Bootstrapper::Bootstrapper everything is peachy.
The code that actually requires the Bootstrapper class is this:
ActiveSupport.on_load :active_record do
require 'bootstrapper/bootstrapper'
end
The source is available here:
http://github.com/jrmehle/bootstrapper/tree/make_gem
Autoload paths actually has an annoying feature of following filesystem paths. For example in your lib or extras (depending on what you autoload) you might have the following file structure:
lib/bootstrapper/bootstrapper.rb
# in this case, Bootstrapper::Bootstrapper.class = Class in rails c
# ie: you don't get a NameError exception
More specifically,
lib/bootstrappers/bootstrapper.rb
# Bootstrapper::Bootstrapper => NameError
# Bootstrappers::Bootstrapper => works
If you really want the other way, you can move everything into your lib/bootstrapper.rb source file but meh, I don't like doing that, that's not how gems are organized. In rails3, you'll find the autoloading pretty nice once you use modules everywhere (which can be painful).
Rails3 uses /extras instead of /lib but it's not required, it's just the default (commented out) from rails new. To switch, you just autoload extras instead of lib.
I have a engine style Rails plugin from which I can create a gem using Jeweler. But when I require it in my Rails environment (or erb) the models within the plugin are not loaded. I have followed a number of tutorials and read just about everything on the subject.
# environment.rb
config.gem 'myengine'
# in irb
require 'myengine'
I have unpacked the gem and verified that all files are present. My init.rb has been moved to a new folder called 'rails' as per. All files in 'lib' are automatically added to the $LOAD_PATH, so require 'myengine' runs lib/myengine.rb. I verified this by putting a puts 'hello' within.
Is it because of the physical presence of plugins in a known place that Rails can add all the models, controller etc. to the relevant load_paths? Do I need to replicate this manually when using a gem?
Would gemspec require_paths be a way of adding additional paths other than lib? I assume however that Rails does not just require every single file, but loads them on demand hence the need for the filename and class name to match?
%w{ models controllers helpers }.each do |dir|
path = File.join(File.dirname(__FILE__), 'app', dir) + '/'
$LOAD_PATH << path
puts 'requiring'
Dir.new(path).entries.each do |file|
if file =~ /\.rb/
puts file
require file
end
end
end
By adding the above to lib/myengine.rb all the models/controllers are required. But like I said in my question this is unlikely to be a good way forward.
Offhand I'd say the part about adding those directories to the search path is right on. What you shouldn't need to do is require each file manually (as you allude to in your last sentence). What Rails does when you reference a non-existent constant is to search for a file with the same name (underscored of course) in the load path.
If for some reason you can not abide by the constraint (think about it long and hard) then you are going to need to dig deeper into Rails and see how the reloading mechanism works so you can tie into it properly in development mode.
The problem was the files (in app) where not being added to the gem because when using Jeweler it only automatically adds files to required_paths which are committed to git.