In ruby, if I do "require foo", is there a way to subsequently determine the name of the module or modules defined in foo.rb?
For example, say I have a ruby file named foo.rb that looks like this:
# foo.rb
module MyModule
def self.summary
"this does something useful"
end
...
end
In another script, after I do "require foo", how can I determine that I now have a module named MyModule?
Ultimate what I'm after is to be able to do something like this:
file = someComputedFileName()
require file
puts "summary of #{file}: #{???::summary}
While I could force myself to make module names and file names identical, I'd rather not. I want a bit more freedom in making short filenames but more expressive module names. However, I am guaranteeing to myself that each file will only define a single module (think: plugins).
I don't know if this is the best solution, but off the top of my head this seems to work:
all_constants = Object.constants
require 'foo'
foo_constants = Object.constants - all_constants
foo_constants should give you only the modules, classes or other constants that were defined by foo.rb.
One approach would be to use ObjectSpace.each_object(Module) to find all defined modules before requiring the file. Then, after you require the file, loop over all defined modules again and see if there are any new ones.
require "set"
old_modules = SortedSet.new
ObjectSpace.each_object(Module) {|m| old_modules.add(m) }
file = someComputedFileName()
require file
new_modules = SortedSet.new
ObjectSpace.each_object(Module) {|m| new_modules.add(m) unless old_modules.include?(m) }
puts "summary of #{file}: #{new_modules.to_a.map{|m|m.summary}.join(',')}"
That would also let you define more than one module in the file.
Related
I've been assigned to perform some maintenance on an existing Ruby gem project. I'm not native to Ruby, but there are files that to me appear to be unnecessary.
Let's say that folder a/b/c is the root of the project, representing module A::B::C. There are also sub modules A::B::C::D1, A::B::C::D2, A::B::C::D3, etc.
The first file that I don't find logical is file modules.rb in folder a/b/c. This contains an empty module declaration for every module in the entire project:
module A::B::C
end
module A::B::C::D1
end
module A::B::C::D2
end
# etc
I tried to find out what this file is for, but I couldn't find any mentions anywhere on Google apart from examples where the modules.rb actually contains all of the code (e.g. https://github.com/shrinidhi99/learn-ruby-for-fun/blob/master/Modules.rb, https://borg.garasilabs.org/andrew/ruby-training/-/blob/master/codes/modules.rb, https://zetcode.com/lang/rubytutorial/oop2/). There's also no reference to it anywhere in the project itself. The only thing it appears to achieve is to provide documentation on rubydoc.info. That can probably be inlined in the separate files.
Besides that, most modules M have a matching file m.rb that sits besides the m folder. For example, file a/b/c.rb, a/b/c/d1.rb, etc. This file contains nothing except require statements of all files in the matching module. That means that file a/b/c.rb also has require statements for a/b/c/d1 etc.
There are two sub modules of A::B::C that are not included in these require files, and these modules have several sub modules of their own. That, combined with the fact that each file should just mention it requirements itself, indicates that these require files are completely unnecessary. The only reason I can think of is mentioned here: https://stackoverflow.com/a/26470550/
Am I wrong in thinking that I can simply remove these files, or are they still necessary? Or is this something that's just "the Ruby way"?
Something like this should work. One file -- one class (or module). If you have namespace and there is general logic in it -- separate file for the namespace
# a.rb
Dir[File.join(__dir__, 'a', '*.rb')].each { |f| require f }
module A
# general A logic here
end
# a/b.rb
Dir[File.join(__dir__, 'b', '*.rb')].each { |f| require f }
module A
module B
# general A::B logic here
end
end
# a/b/c.rb
module A
module B
module C
end
end
end
# a/b/d.rb
module A
module B
module D
end
end
end
# x.rb
require_relative 'a'
class X
include A::B::C
end
I want to be able to statically analyze my code. That is, to know from the plain text of the file where every function and variable comes from. IDEs and text editor plugins work better when they can trace the origin of every symbol as well.
So for example, if I have application code like this:
#...
Y.some_method()
#...
Then I want to see Y in an include/import/require/extend/def statement somewhere on the page.
In other languages I use, one can explicitly choose which sub-parts of a namespace to bring in to the current context.
Python:
from X import Y
Haskell:
import X (Y)
Elixir:
alias X.Y, as: Y
And while it's possible to import all contained names in Python, the "wildcard import" is frowned upon:
from X import *
". . . they make it unclear which names are present in the namespace, confusing both readers and many automated tools."
In Ruby, it seems that this fully implicit "wildcard" way is the only way to bring in a contained name:
include X
This makes Y available, but is there some way to make this explicit? The docs for Ruby include don't show any options.
What I'd really like to do in Ruby is something like one of these:
from X include Y
include X::Y as Y
The best I've come up with so far is:
require 'x/y' ; Y = X::Y
Here's a crazy hack in the answer to another question which would enable this.
Try this. But I agree with #tadman that you should consider doing it in the Ruby way.
Object.define_singleton_method(:include) do |*mths, from: nil|
mod = from || mths.first
mod = mod.dup
if from
all_mths = mod.instance_methods
(all_mths - mths).each { |mth| mod.send :undef_method, mth }
end
super(mod)
end
module Foobar
def foo
puts :foo
end
def bar
puts :bar
end
end
class Abc
include Foobar
end
Abc.new.foo # => 'foo'
Abc.new.bar # => 'foo'
class AbcWithoutBar
include :foo, from: Foobar
end
AbcWithoutBar.new.foo # => 'foo'
AbcWithoutBar.new.bar # => NoMethodError
Ruby always executes the code that you require
And since there is no partial execution of a file there cannot be partial require.
When you require a feature Ruby locates the corresponding file using the load paths in $: and then double checks against the list of loaded files in $" and if the file has not yet been loaded executes the file.
Ruby is a dynamic language, the best way to reason about its source code is halting a running program rather than statically. In fact even class and def are not declarations but just method calls that are executed at runtime. Consider for example this contrived example
class Surprise < [Array, Hash, Fixnum, Object].sample
end
If you want to know where a method or class has been defined best use pry. You can require pry and then use binding.pry to stop anywhere in your source code and spelunk around to inspect objects and source code. Two of the most useful commands are ls and $
ls prints all methods of an object or class
$ prints the file location and source code of a method
In my Rails application I have a file sample_data.rb inside /lib/tasks as well as a bunch of test files inside my /spec directory.
All these files often share common functionality such as:
def random_address
[Faker::Address.street_address, Faker::Address.city].join("\n")
end
Where should I put those helper functions? Is there some sort of convention on this?
Thanks for any help!
You could create a static class, with static functions. That would look something like this:
class HelperFunctions
def self.random_address
[Faker::Address.street_address, Faker::Address.city].join("\n")
end
def self.otherFunction
end
end
Then, all you would need to do is:
include your helper class in the file you want to use
execute it like:
HelperFunctions::random_address(anyParametersYouMightHave)
When doing this, make sure you include any dependencies in your HelperFunctions class.
If you're sure it's rake only specific, you also can add in directly in RAILS_ROOT/Rakefile (that's probably not the case for the example you use).
I use this to simplify rake's invoke syntax :
#!/usr/bin/env rake
# Add your own tasks in files placed in lib/tasks ending in .rake,
# for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.
require File.expand_path('../config/application', __FILE__)
def invoke( task_name )
Rake::Task[ task_name ].invoke
end
MyApp::Application.load_tasks
That way, I can use invoke "my_namespace:my_task" in rake tasks instead of Rake::Task[ "my_namespace:my_task" ].invoke.
You share methods in a module, and you place such a module inside the lib folder.
Something like lib/fake_data.rb containing
module FakeData
def random_address
[Faker::Address.street_address, Faker::Address.city].join("\n")
end
module_function
end
and inside your rake task just require the module, and call FakeData.random_address.
But, if it is like a seed you need to do every time you run your tests, you should consider adding this to your general before all.
E.g. my spec_helper looks like this:
# Requires supporting ruby files with custom matchers and macros, etc,
# in spec/support/ and its subdirectories.
Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }
RSpec.configure do |config|
config.use_transactional_fixtures = true
config.infer_base_class_for_anonymous_controllers = false
config.order = "random"
include SetupSupport
config.before(:all) do
load_db_seed
end
end
and the module SetupSupport is defined in spec/support/setup_support.rb and looks as follows:
module SetupSupport
def load_db_seed
load(File.join(Rails.root, 'db', 'seeds.rb'))
end
end
Not sure if you need to load the seeds, or are already doing this, but this is the ideal spot to also generate needed fake data.
Note that my setup support class is defined in spec/support because the code is only relevant to my specs, I have no rake task also needing the same code.
I have to Ruby files: one contains a module with some methods for statistical calculation, in the other file I want to call one of the methods in the module.
How can I do that in Ruby?
Is that the right way?
require 'name of the file with the module'
a=[1,2,3,4]
a.method1
Require needs the absolute path to the file unless the file is located in one of Ruby's load paths. You can view the default load paths with puts $:. It is common to do one of the following to load a file:
Add the main file's directory to the load path and then use relative paths with require:
$: << File.dirname(__FILE__)
require "my_module"
Ruby 1.8 code that only loads a single file will often contain a one-liner like:
require File.expand_path("../my_module", __FILE__)
Ruby 1.9 added require_relative:
require_relative "my_module"
In the module you will need to define the methods as class methods, or use Module#module_function:
module MyModule
def self.method1 ary
...
end
def method2
...
end
module_function :method2
end
a = [1,2,3,4]
MyModule.method1(a)
Your way is correct if your module file is in the require search path.
If your module provide methods to be used by the object itself, you must do:
require 'name of the file with the module'
a=[1,2,3,4]
a.extend MyModule # here "a" can use the methods of MyModule
a.method1
See Object#extend.
Otherwise, if you'll use the methods directly by the module, you'll use:
MyModule.method1(a)
I've placed a set of .rb files in a directory modules/. Each of these files contains a module. I'm loading all of these files from a separate script with this:
Dir["modules/*.rb"].each {|file| load file }
But then I have to include them, one by one, listing and naming each of them explicitly:
class Foo
include ModuleA
include ModuleB
# ... and so on.
end
I'm wondering if there is some non-explicit one-liner that can accomplish this, a la (pseudocode) ...
class Foo
for each loaded file
include the module(s) within that file
end
# ... other stuff.
end
I've considered actually reading the files' contents, searching for the string "module", and then extracting the module name, and somehow doing the include based on that -- but that seems ridiculous.
Is what I'm trying to do advisable and/or possible?
You can manually define some variable in each of your file and then check for its value while including the file.
For example, module1.rb:
export = ["MyModule"]
module MyModule
end
And the second one, module2.rb:
export = ["AnotherModule", "ThirdModule"]
module AnotherModule
end
module ThirdModule
end
And then just include all of them in your file (just the idea, it may not work correctly):
class Foo
Dir["modules/*.rb"].each do |file|
load file
if export != nil
export.each do { |m| include(Kernel.const_get(m))
end
end
end
I would expect it to be possible since you can place ruby code below class and include is also just a ruby call but you have to think of which module needs to be included where since your code is not the only one that loads and includes modules. And you wil not want to include all modules from the object space in your class.
So i personally would include them by name - you are adding funcionality to a class and by naming each module you document what is being added where.
And if you want this one liner: put a code in each module that adds its name to global list (remembering the disadvantages if using globals at all) and then iterate this list in the class definition to include all of them or part based on a criterium like name or what.