Where's That Method Defined?
When you're just getting familiar with Ruby, it can be overwhelming trying to figure out where methods are defined. A given method could have been defined by your own app, a gem, or by Ruby itself.
For example, an array responds to from:
['a', 'b', 'c'].from(1)
=> ["b", "c"]
Where is from from? Use the method method!
['a', 'b', 'c'].method(:from)
=> #<Method: Array#from(position) ~/.rvm/gems/ruby-2.7.2/gems/activesupport-6.1.4/lib/active_support/core_ext/array/access.rb:12>
from is added into Array by ActiveSupport.
For core Ruby methods, calling method won't point you to the source code. But the name that is provided is usually enough to get you to the right documentation.
[].method(:pop)
=> #<Method: Array#pop(*)>
pop is a part of the Array class.
[].method(:detect)
=> #<Method: Array(Enumerable)#detect(*)>
detect is a part of the Enumerable module that is included in Array.
If a method is just an alias for another method, then method isn't going to help us figure out where that alias was defined:
[].method(:blank?)
=> #<Method: Array#blank?(empty?)()>
In this case, we just have to search through ActiveSupport to see that it sets up blank? as an alias for empty?.
References
