I'm trying to pick up ruby by porting a medium-sized (non-OO) perl program. One of my personal idioms is to set options like this:
use Getopt::Std;
our $opt_v; # be verbose
getopts('v');
# and later ...
$opt_v && print "something interesting\n";
In perl, I kind of grit my teeth and let $opt_v be (effectively) a global.
In ruby,the more-or-less exact equivalent would be
require 'optparse'
opts.on("-v", "--[no-]verbose", TrueClass, "Run verbosely") {
|$opt_verbose|
}
opts.parse!
end
where $opt_verbose is a global that classes could access. Having classes know about global flags like that seems ... er ... wrong. What's the OO-idiomatic way of doing this?
- Let the main routine take care of all option-related stuff and have the classes just return things to it that it decides how to deal with?
- Have classes implement optional behaviour (e.g., know how to be verbose) and set a mode via an attr_writer sort of thing?
updated: Thanks for the answers suggesting optparse, but I should have been clearer that it's not how to process command-line options I'm asking about, but more the relationship between command-line options that effectively set a global program state and classes that should ideally be independent of that sort of thing.
-
The first hit on google for "processing command line options in ruby" is an article about Trollop which seems to be a good tool for this job.
From John -
The optparse library is part of the standard distribution, so you'll be able to use it without requiring any third party stuff.
I haven't used it personally, but rails seems to use it extensively and so does rspec, which I guess is a pretty solid vote of confidence
This example from rails'
script/consoleseems to show how to use it pretty easily and nicelyFrom Orion Edwards -
A while back I ran across this blog post (by Todd Werth) which presented a rather lengthy skeleton for command-line scripts in Ruby. His skeleton uses a hybrid approach in which the application code is encapsulated in an application class which is instantiated, then executed by calling a "run" method on the application object. This allowed the options to be stored in a class-wide instance variable so that all methods in the application object can access them without exposing them to any other objects that might be used in the script.
I would lean toward using this technique, where the options are contained in one object and use either attr_writers or option parameters on method calls to pass relevant options to any additional objects. This way, any code contained in external classes can be isolated from the options themselves -- no need to worry about the naming of the variables in the main routine from within the
thingyclass if your options are set with athingy.verbose=trueattr_writer orthingy.process(true)call.From Nathan Fritz
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