How can I pass named arguments to a Rake task?

ruby arguments rake task named-parameters
Andrew picture Andrew · Feb 23, 2011 · Viewed 7.4k times · Source

Is there a way to pass named arguments to a Rake task without using environment variables?

I am aware that Rake tasks can accept arguments in two formats:

Environment Variables

$ rake my_task foo=bar

This creates an environment variable with the name foo and the value bar that can be accessed in the Rake task my_task by ENV['foo'].

Rake Task Arguments

$ rake my_task['foo','bar']

This passes the values foo and bar to the first two task arguments (if they are defined). If my_task were defined as:

task :my_task, :argument_1, :argument_2

then argument_1 would have the value foo and argument_2 would have the value bar.

Answer

mu is too short picture mu is too short · Feb 23, 2011

You can say things like this:

rake some_task -- --arg=value

And then, inside your task, ARGV will be

[ 'some_task', '--arg=value' ]

so you could use OptionParser (or some other option parser) to unpack ARGV just like in any old CLI script; the funny looking -- is necessary to keep rake from trying to parse --arg=like as a rake switch.

You're probably better off with the standard environment variable approach, it isn't as ugly as all the -- stuff and it is the usual way of passing arguments to rake tasks.

Related questions

How do I pass multiple arguments to a ruby method as an array?

I have a method in a rails helper file like this def table_for(collection, *args) options = args.extract_options! ... end and I want to be able to call this method like this args = [:name, :description, :start_date, :end_date] …

Read More
How do you specify a required switch (not argument) with Ruby OptionParser?

I'm writing a script and I want to require a --host switch with value, but if the --host switch isn't specified, I want the option parsing to fail. I can't seem to figure out how to do that. The docs …

Read More
ruby convert array into function arguments

Say I have an array. I wish to pass the array to a function. The function, however, expects two arguments. Is there a way to on the fly convert the array into 2 arguments? For example: a = [0,1,2,3,4] b = [2,3] a.slice(b) …

Read More