How do I use Ruby metaprogramming to refactor this common code?
I inherited a project with a lot of badly-written Rake tasks that I need to clean up a bit. Because the Rakefiles are enormous and often prone to bizarre nonsensical dependencies, I'm simplifying and isolating things a bit by refactoring everything to classes.
Specifically, that pattern is the following:
namespace :foobar do
desc "Frozz the foobar."
task :frozzify do
unless Rake.application.lookup('_frozzify')
require 'tasks/foobar'
Foobar.new.frozzify
end
Rake.application['_frozzify'].invoke
end
# Above pattern repeats many times.
end
# Several namespaces, each with tasks that follow this pattern.
In tasks/foobar.rb
, I have something that looks like this:
class Foobar
def frozzify()
# The real work happens here.
end
# ... Other tasks also in the :foobar namespace.
end
For me, this is great, because it allows me to separate the task dependencies from each other and to move them to another location entirely, and I've been able to drastically simplify things and isolate the dependencies. The Rakefile doesn't hit a require
until you actually try to run a task. Previously this was causing serious issues because you couldn't even list the tasks without it blowing up.
My problem is that I'm repeating this idiom very frequently. Notice the following patterns:
For every namespace
:xyz_abc
, there is a corresponding class intasks/...
in the filetasks/[namespace].rb
, with a class name that looks likeXyzAbc
.For every task in a particular namespace, there is an identically named method in the associated namespace class. For example, if namespace
:foo_bar
has a task:apples
, you would expect to seedef apples() ...
inside theFooBar
class, which itself is intasks/foo_bar.rb
.Every task
:t
defines a "meta-task"_t
(that is, the task name prefixed w开发者_StackOverflow社区ith an underscore) which is used to do the actual work.
I still want to be able to specify a desc
-description for the tasks I define, and that will be different for each task. And, of course, I have a small number of tasks that don't follow the above pattern at all, so I'll be specifying those manually in my Rakefile.
I'm sure that this can be refactored in some way so that I don't have to keep repeating the same idiom over and over, but I lack the experience to see how it could be done. Can someone give me an assist?
Something like this should work for you.
# Declaration of all namespaces with associated tasks.
task_lists = {
:foobar => {
:task_one => "Description one",
:task_two => "Description two",
:frozzify => "Frozz the foobar",
:task_three => "Description three" },
:namespace_two => {
:task_four => "Description four",
:etc => "..."} }
# For every namespace with list of tasks...
task_lists.each do |ns, tasks|
# In the given the namespace...
namespace ns do
# For every task in the task list...
tasks.each do |task_name, description|
# Set the task description.
desc description
# Define the task.
task task_name do
unless Rake.application.lookup("_#{task_name}")
# Require the external file identified by the namespace.
require "tasks/#{ns}"
# Convert the namespace to a class name and retrieve its associated
# constant (:foo_bar will be converted to FooBar).
klass = Object.const_get(ns.to_s.gsub(/(^|_)(.)/) { $2.upcase })
# Create a new instance of the class and invoke the method
# identified by the current task.
klass.new.send(task_name)
end
Rake.application["_#{task_name}"].invoke
end
end
end
end
Update: added descriptions.
(Note that I haven't tested it, so there might be small errors in there.)
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