How to Add 'Each' Method to Ruby Object (Or Should I Extend Array)

How do I add 'each' method to Ruby object (or should I extend Array)?

For the general case of implementing array-like methods, yes, you have to implement them yourself. Vava's answer shows one example of this. In the case you gave, though, what you really want to do is delegate the task of handling each (and maybe some other methods) to the contained array, and that can be automated.

require 'forwardable'

class Results
  include Enumerable
  extend Forwardable
  def_delegators :@result_array, :each, :<<
end

This class will get all of Array's Enumerable behavior as well as the Array << operator and it will all go through the inner array.

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Note, that when you switch your code from Array inheritance to this trick, your << methods would start to return not the object intself, like real Array's << did -- this can cost you declaring another variable everytime you use <<.

Possible to extend methods of Array in ruby?

Yes, this is possible.

class Array
  def join_names
    collect(&:name).join(", ")
  end
end

But this makes it more likely that you code will have namespace collisions with other libraries that add methods to the Array class.

Ruby: How do I add methods to Object? (or simply Extend the object class)

# object.rb
class Object
  def table_name
    self.class.name.tableize
  end
end

put it into /config/initializers or into lib folder (in this case you'll need to include it in ApplicationController).

Ruby Extended Array class that supports full method chain

If you ever want to monkey-patch a core class but you think it's icky, you should remember that refinements are made just for this scenario.

module ArrayWithWord
  refine Array do
    def word
      [*self[0..1],*self[-2..-1]].map(&:chr).join
    end
  end
end

class WordTest
  using ArrayWithWord

  # [].word works here
  def self.sort_transform(a)
    [
      a.word,
      a.sort.word,
      a.sort_by(&:-@).word,
      a.map(&:chr).sort.map(&:ord).word
    ].join ?-
  end
end

WordTest.sort_transform(%w(foo bar baz quux))
# => "fbbq-bbfq-bbfq-bbfq"

# [].word doesn't work here
[].word
# => NoMethodError (undefined method `word' for []:Array)

Using each for object with an array of objects

In ruby we do chain methods to accomplish different complicated transforms:

@cars.map do |car|
  [car.id, car.mileage]
end.each do |id, mileage|
    ...
end

Can I add object to an array in a loop and then return the array in the same line?

barcodes = Array.new(count){ Barcode.create }

Call method of an object in an array

So the problem is in your implementation of StockList. You have extended the class array but are setting up a new instance variable @stockList. When you call addStock you are adding an instance to the @stockList variable. But when you call each on the StockList instance, it is not iterating over the StockList.

Conceivably, you could add a method each to StockList like:


def each(&block)
@stockList.each(&block)
end


and it should work.

But really I would recommend rethinking your data structures. StockList should really not extend Array.

Ruby Array Extension

Extending Array means that you should be using self rather than passing in an array. Right now, you're summing an empty array (from the default parameter) rather than the array that #sum is called on.

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