Strings in Ruby have an instance method namely split that splits the given String and returns an array of substrings based on the separator given as an argument to it.

have a look at these examples:

gauravjhadiyal@gauravjhadiyal:~$ irb
2.1.5 :001 > "this-is-a-ruby-string".split("-")
 => ["this", "is", "a", "ruby", "string"] 
2.1.5 :002 > "another/example".split("/")
 => ["another", "example"] 
2.1.5 :003 > "second example for rubyists".split(" ")
 => ["second", "example", "for", "rubyists"] 

find_index instance method of Array returns the first index of the given parameter depending on the presence of it within the array.

2.1.5 :004 > ["1","45","23","12"].find_index("12")
 => 3 
2.1.5 :005 > ["1","45","23","12"].find_index("11")
 => nil 

map method is also an instance method available with Array .It simply iterates through an array ,passes each element to a block and creates a brand-new-array accumulating all the values returned from the block.

2.1.5 :007 > squares = [7,2,19,23].map { |number| number ** 2}
 => [49, 4, 361, 529] 
2.1.5 :008 > p squares
[49, 4, 361, 529]
 => [49, 4, 361, 529] 

The internal implementation of map method looks akin to this:

class Array
  def map
     output = []
     self.each do |item|
        output << yield(item)
     end
     output
  end
end

and lastly,capitalize method works like this:

2.1.5 :011 > "sample_string".capitalize
 => "Sample_string" 
2.1.5 :012 > "string".capitalize
 => "String" 

Thanks a lot for Reading.