- Slicing an Array
- Iterating over an Array
- Creating Enumerable Classes
- Sorting an Array
- Iterating over Nested Arrays
- Modifying All the Values in an Array
- Sorting Nested Arrays
- Building a Hash from a Config File
- Sorting a Hash by Key or Value
- Eliminating Duplicate Data from Arrays (Sets)
- Working with Nested Sets
This chapter is from the book
This chapter is from the book
This chapter is from the book
Creating Enumerable Classes
You may find that you need to make information in a given, custom data structure available to the rest of the world. In such a case, if the data structure that you have created to store arbitrary objects implements an #each method, the Enumerable mix-in will allow anyone who uses your class to access several traversal and searching methods, for free.
require 'enumerator'
class NumberStore
include Enumerable
attr_reader :neg_nums, :pos_nums
def add foo_object
if foo_object.respond_to? :to_i
foo_i = foo_object.to_i
if foo_i < 0
@neg_nums.push foo_i
else
@pos_nums.push foo_i
end
else
raise "Not a number."
end
end
def each
@neg_nums.each { |i| yield i }
@pos_nums.each { |i| yield i }
end
def initialize
@neg_nums = []
@pos_nums = []
end
end
mystore = NumberStore.new
mystore.add 5
mystore.add 87
mystore.add(-92)
mystore.add(-1)
p mystore.neg_nums
p mystore.pos_nums
p mystore.grep -50..60
Produces:
[-92, -1] [5, 87] [-1, 5]
In the above contrived example, I have created a data structure called NumberStore which stores negative numbers in one list and positive numbers in another list. Because the #each method is implemented, methods like #find, #select, #map, and #grep become available. In the last line of the code sample I use the mixed-in method #grep to find numbers stored in mystore that are between 50 and 60.