How do I get method signatures or method descriptions in Ruby's irb?

Question

I'm wondering if Ruby's irb has the ability to supply method/function signatures or descriptions.

I know I can do something like this in the irb

[].methods.sort

and get all the methods/functions available to arrays but how can I get more information(while in the irb) about specific methods/functions?

Answer 1

You can use #method and then use Method methods:

1.method(:+).arity
# => 1
1.method(:+).parameters
# => [[:req]]
[].method(:reduce).parameters
# => [[:rest]]