I am working on a project where the current developers have put their "Plain Old Ruby Objects" in the models directory of our Rails app.
I have seen most examples online where the PORO files go inside lib instead, but some say models.
Is there even a logical / specific reason why people put them in the models directory over the lib directory?
"Idiomatically" the models directory intended for code used to hold state. Most of the time this would be ActiveRecord subclasses corresponding to database tables. However frequently people put other stuff in the models directory. One thing often seen are code dropped here in order to take advantage of auto-reloading. (the lib dir doesn't normally auto-reload)
Based on the Getting Started Rails guide, the app/models/ directory is pretty much anything, whereas lib/ is for modules that are used across the entire app (e.g. extensions).
As #seand said, yes, one advantage is that the app/models/ directory automatically reloads, but I tend to think of it as any class that "interacts with other classes" should live in app/models/, with the only exception being a service class (which I tend to think of as "a class which manipulates the state of another class"), which I tend to put into app/services/.
I know a lot of developers would disagree with me - many I've talked to even create a separate directory namespaced to their app (e.g. if your app is named "MyBlog", they would create an app/myblog directory for any object not explicitly backed by the database, but not a module or a service class either.
That said, I think ultimately it boils down to a) personal preference and b) where you feel is best to place the PORO with respect to your app.
There is no hard and fast rule on where to put POROs. The rails community has been hashing this out for a while now. At one point the convention was to put stuff in the concerns directory but that seems to have fallen out of favor with some folks.
One rule of thumb for the difference between /lib and app/{blah} is that code in the /lib folder is code that you presumably can reuse across several projects e.g. general purpose class or utilities. for example if you have some custom monkey patches to core ruby or rails classes that you will use in multiple projects, a good place to but them would be in the lib folder. Anything in app/{blah} should pertain specifically to current project.
One way to think of lib folder is as the poor cousin of plugins and gems.
Just my 2 cents on the subject
I feel like I understand the difference between require and require_dependency (from How are require, require_dependency and constants reloading related in Rails?).
However, I'm wondering what should happen if I use some of the various methods out there (see http://hemju.com/2010/09/22/rails-3-quicktip-autoload-lib-directory-including-all-subdirectories/ and Best way to load module/class from lib folder in Rails 3?) to get all files loading so we:
don't need to use require_dependency all over the place in the application and
don't have to restart development servers when files in the lib directory change.
It seems like development performance would be slightly impacted, which is not that big of a deal to me. How would performance be impacted in a production environment? Do all of the files generally get loaded only once if you are in production anyway? Is there a better way that I'm not seeing?
If you could include some resources where I could read more about this, they would be greatly appreciated. Some blog posts said that this behavior changed recently with Rails 3 for autoreloading lib/* files and that it was contentious, but I didn't see any links to these discussions. It would be helpful for considering the pros/cons. Thanks!
The code reloader is disabled by default in production. So if you are calling require_dependency at the top of a file it is going to be executed only once.
The Rails 3 change you mentioned is really small. You can usually call Foo and it will be loaded from app/models/foo.rb automatically. Before it could also be loaded from lib/foo.rb. (These directories app/models and lib are called autoload paths.) Rails team decided to remove lib from autoload paths in the 3rd version. You can still put it back. But it is encouraged to leave in lib less frequenttly-changed and project-specific files. If you have something that does not belong to any of the default app subdirectories like app/models or app/controllers you don't have to put it in lib. You can add your own subdirectory. I have app/presenters, for example. There is a discussion on the old issue tracker if you want more info on that.
Where's the recommended location for libraries in Rails 3? Is it as simple as 'lib'?
I'm not sure because 'lib' seems more like a Rails 2 remnant, especially considering that it's no longer auto-loaded (and there was a lot of discussion about that, apparently).
Initializers are more for (obviously) initialization tasks such as overrides.
Specifically I have a small module for attachment handling (Paperclip doesn't fit here) that's too large and distinct to include in my model, but not generic or worthwhile enough to implement as a gem.
From a functionality standpoint it lives somewhere in the middle among the model, view, and controller. This makes it sound like a helper, but in Rails helpers are intended for views AFAIK.
Should I just put it in 'lib' and autoload it in application.rb? Or maybe I could create a custom form builder to handle the presentation (or both).
I know how to make it work, but I'm hoping to learn something new. :)
lib is still the right place to put these kind of things.
Autoloading lib was removed in Rails 3 because of the way engines work, but mainly because it's easy to just add it to the autoload_paths if you do want it automatically loaded and if not, you can require as needed. lib is still in the load path, so you don't need to specify where the module or class you're requiring is.
You're correct, helpers are intended for the view, and would not be the place to put any model-related logic.
I'd put the module in lib, and require and include it in your model as needed.
What are the reasons putting a module in /helpers over the /lib folder in a RoR app?
Are /helpers more controller specific, while the /lib is more general in nature?
I think this is a good question because the MVC notion makes us forget that it's all really just metaphors for us to organize code so we don't get too mixed up. If you need to do some simple formating go with a helper, otherwise probably a module in /lib.
Helpers are strictly for defining methods that you want available in your views. /lib modules can be used for anything and are available throughout the application.
Since the latest Rails 3 release is not auto-loading modules and classes from lib anymore,
what would be the best way to load them?
From github:
A few changes were done in this commit:
Do not autoload code in *lib* for applications (now you need to explicitly
require them). This makes an application behave closer to an engine
(code in lib is still autoloaded for plugins);
As of Rails 2.3.9, there is a setting in config/application.rb in which you can specify directories that contain files you want autoloaded.
From application.rb:
# Custom directories with classes and modules you want to be autoloadable.
# config.autoload_paths += %W(#{config.root}/extras)
# Autoload lib/ folder including all subdirectories
config.autoload_paths += Dir["#{config.root}/lib/**/"]
Source: Rails 3 Quicktip: Autoload lib directory including all subdirectories, avoid lazy loading
Please mind that files contained in the lib folder are only loaded when the server is started. If you want the comfort to autoreload those files, read: Rails 3 Quicktip: Auto reload lib folders in development mode. Be aware that this is not meant for a production environment since the permanent reload slows down the machine.
The magic of autoloading stuff
I think the option controlling the folders from which autoloading stuff gets done has been sufficiently covered in other answers. However, in case someone else is having trouble stuff loaded though they've had their autoload paths modified as required, then this answer tries to explain what is the magic behind this autoload thing.
So when it comes to loading stuff from subdirectories there's a gotcha or a convention you should be aware. Sometimes the Ruby/Rails magic (this time mostly Rails) can make it difficult to understand why something is happening. Any module declared in the autoload paths will only be loaded if the module name corresponds to the parent directory name. So in case you try to put into lib/my_stuff/bar.rb something like:
module Foo
class Bar
end
end
It will not be loaded automagically. Then again if you rename the parent dir to foo thus hosting your module at path: lib/foo/bar.rb. It will be there for you. Another option is to name the file you want autoloaded by the module name. Obviously there can only be one file by that name then. In case you need to split your stuff into many files you could of course use that one file to require other files, but I don't recommend that, because then when on development mode and you modify those other files then Rails is unable to automagically reload them for you. But if you really want you could have one file by the module name that then specifies the actual files required to use the module. So you could have two files: lib/my_stuff/bar.rb and lib/my_stuff/foo.rb and the former being the same as above and the latter containing a single line: require "bar" and that would work just the same.
P.S. I feel compelled to add one more important thing. As of lately, whenever I want to have something in the lib directory that needs to get autoloaded, I tend to start thinking that if this is something that I'm actually developing specifically for this project (which it usually is, it might some day turn into a "static" snippet of code used in many projects or a git submodule, etc.. in which case it definitely should be in the lib folder) then perhaps its place is not in the lib folder at all. Perhaps it should be in a subfolder under the app folder· I have a feeling that this is the new rails way of doing things. Obviously, the same magic is in work wherever in you autoload paths you put your stuff in so it's good to these things. Anyway, this is just my thoughts on the subject. You are free to disagree. :)
UPDATE: About the type of magic..
As severin pointed out in his comment, the core "autoload a module mechanism" sure is part of Ruby, but the autoload paths stuff isn't. You don't need Rails to do autoload :Foo, File.join(Rails.root, "lib", "my_stuff", "bar"). And when you would try to reference the module Foo for the first time then it would be loaded for you. However what Rails does is it gives us a way to try and load stuff automagically from registered folders and this has been implemented in such a way that it needs to assume something about the naming conventions. If it had not been implemented like that, then every time you reference something that's not currently loaded it would have to go through all of the files in all of the autoload folders and check if any of them contains what you were trying to reference. This in turn would defeat the idea of autoloading and autoreloading. However, with these conventions in place it can deduct from the module/class your trying to load where that might be defined and just load that.
Warning: if you want to load the 'monkey patch' or 'open class' from your 'lib' folder, don't use the 'autoload' approach!!!
"config.autoload_paths" approach: only works if you are loading a class that defined only in ONE place. If some class has been already defined somewhere else, then you can't load it again by this approach.
"config/initializer/load_rb_file.rb" approach: always works! whatever the target class is a new class or an "open class" or "monkey patch" for existing class, it always works!
For more details , see: https://stackoverflow.com/a/6797707/445908
Very similar, but I think this is a little more elegant:
config.autoload_paths += Dir["#{config.root}/lib", "#{config.root}/lib/**/"]
In my case I was trying to simply load a file directly under the lib dir.
Within application.rb...
require '/lib/this_file.rb'
wasn't working, even in console and then when I tried
require './lib/this_file.rb'
and rails loads the file perfectly.
I'm still pretty noob and I'm not sure why this works but it works. If someone would like to explain it to me I'd appreciate it :D I hope this helps someone either way.
I had the same problem. Here is how I solved it. The solution loads the lib directory and all the subdirectories (not only the direct). Of course you can use this for all directories.
# application.rb
config.autoload_paths += %W(#{config.root}/lib)
config.autoload_paths += Dir["#{config.root}/lib/**/"]
As of Rails 5, it is recommended to put the lib folder under app directory or instead create other meaningful name spaces for the folder as services , presenters, features etc and put it under app directory for auto loading by rails.
Please check this GitHub Discussion Link as well.
config.autoload_paths does not work for me. I solve it in other way
Ruby on rails 3 do not automatic reload (autoload) code from /lib folder. I solve it by putting inside ApplicationController
Dir["lib/**/*.rb"].each do |path|
require_dependency path
end
If only certain files need access to the modules in lib, just add a require statement to the files that need it. For example, if one model needs to access one module, add:
require 'mymodule'
at the top of the model.rb file.
Spell the filename correctly.
Seriously. I battled with a class for an hour because the class was Governance::ArchitectureBoard and the file was in lib/governance/architecture_baord.rb (transposed O and A in "board")
Seems obvious in retrospect, but it was the devil tracking that down. If the class is not defined in the file that Rails expects it to be in based on munging the class name, it is simply not going to find it.
There are several reasons you could have problems loading from lib - see here for details - http://www.williambharding.com/blog/technology/rails-3-autoload-modules-and-classes-in-production/
fix autoload path
threadsafe related
naming relating
...