🎩 Fancy to_proc

Have you ever wished Symbol#to_proc was chainable and took arguments?

["banana  ", " hammock!"].map &:strip&:capitalize&:gsub.(/mm/, "dd")
#=> ["Banana", "Haddock!"]

Well now it can! Read on to see how to use it, or even better read my post explaining how it works with pictures.

The ampersand operator is added to Symbol, Proc and Method so that you can chain like so:

["banana", "  hammock! "].map &:strip&:capitalize
#=> ["Banana", "Hammock!"]

Note that above the first ampersand is built into Ruby, it's the second ampersand added by this Gem.

You can also use the method method to get a method and use that as a proc in a chain...

["banana", "hammock"].map &method(:p)&:upcase
#-> "banana"
#-> "hammock"
#=> ["BANANA", "HAMMOCK"]

Yep, pass whatever arguments you like to your symbol method, very convenient!

["banana", "hammock!"].map &:gsub.(/mm/, "dd")
#=> ["banana", "haddock!"]

Note the dot before the brackets; it's short for .call() which you can also use. Unlike in Proc we can't use square brackets for a call alias [] as this is used by Symbol for element referencing already.

I'm not sure how I feel about these methods. They have their uses and they're not too crazy, but they're still a bit unintuitive and weird. As such I'm calling them experimental and may remove / change them. Feedback please! Also note that if you're already defining any of the methods in this gem then they won't be clobbered.

Instead of the method being called on the yielded object, the object(s) is passed to the method. How often have you wanted to do this:

["potato", "scrunchie"].map &~:p
#=> "potato"
#=> "scrunchie"

Note; this is the unary tilde, so while it comes before it's just a method called on Symbol. It can only look up methods on Symbol but that includes things from Kernel like p and puts, but it's otherwise limited. Also due to operator precedence it needs wrapping in brackets if you want to chain.

Invokes the square brackets element reference method on Array or Hash.

[["banana"], ["hammock"]].map &[0] # works on Array or Hash
[{ thing: "banana" }, { thing: "hammock" }].map &[:thing]

#=> ["banana", "hammock"]

Pass a single argument to a symbol method, slightly shorter than the above call brackets style. Specifically designed for this kind of case:

[1, 2, 3, 4].map &:*|2
#=> [2, 4, 6, 8]

It returns a proc you can store and reuse (very terse):

inc = :+|1
[1, 2, 3, 4].map &inc
#=> [2, 3, 4, 5]

It doesn't have to be used for maths though:

["chocolate", "doorstop?"].map &:delete|"?"
#=> ["chocolate", "doorstop"]

To be used in combination with method tilde. It curries the method and partially applies a value to it. Best see an example:

["nougat", "lightbulb"].each_with_index.map &~:sprintf|"Tasty: %s, Option: %d"
#=> ["Tasty: nougat, Option: 0", "Tasty: lightbulb, Option: 1"]

The above is functionally equivalent to this:

["nougat", "lightbulb"].each_with_index.map &method(:sprintf).curry(2)["Tasty: %s, Option: %d"]
#=> ["Tasty: nougat, Option: 0", "Tasty: lightbulb, Option: 1"]

The pipe syntax is weird but .() is already defined on Proc so I couldn't use it. I'm also not sure how often this will be useful, though I'm sure I've wanted to do something like this on occasion.

Note that if you start chaining expressions with the pipe method in then you'll have to wrap them in brackets because the precedence of pipe isn't high enough. Another reason why these are experimental.

Add this line to your application's Gemfile:

gem "fancy_to_proc"

And then execute:

$ bundle

Or install it yourself as:

$ gem install fancy_to_proc

RuboCop will complain if you don't put spaces around & so I've provided a monkeypatch (yay) to RuboCop's "SpaceAroundOperators" cop to ignore just the &.

To use project-wide require fancy_to_proc at the top of your .rubocop.yml:

require: fancy_to_proc

Or to use on the command line require it with a flag:

rubocop --require fancy_to_proc

Run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release to create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

1. Fork it ( https://github.com/sfcgeorge/fancy_to_proc/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

(and/or open issues, your feedback welcome)