enumerables

Enumerables Ginger Griffis

Tuesday, August 13, 13

Enumerable is a Module Mixin


What the eff is that??


What is a Module?

• A Module is a collection of methods and constants.

• Similar to a regular Class but without the concept of instantiation

• Used as a standalone entity, it can help with namespacing


So..What is a Mixin?

• A Mixin is a Module

• A SPECIAL type of Module


Special How?

• A Mixin happens when you include a Module within a Class

• Instance Methods come to life!

• Allows a sense of multiple inheritance

• 2 objects marry and the result is greater than the sum of the parts


So, as I was saying, Enumerable is a Module Mixin

• Provides Collection type classes with traversal, searching, and sorting functionality


Examples in Standard Ruby Library

• Some of your BFFs include Enumerable

• Array, Hash, Set

• Range, File


Some Cool Enumerable Methods

• all? (do all items return true for the block)

• any? (do any items return true for the block)

• collect (make new collection with results)

• count

• detect (return the first item that returns true for the block)

• find

• first

• grep (return all items that === a pattern)

• inject (iterates through the collection with an accumulator)

• reject (returns all items that return false for the block)

• select (returns all items that return true for the block)


Methods that must be defined if a class includes Enumerable

• each (basically some flavor of yielding to a block for each element in your object)

• If the class wishes to use the max, min, or sort functions provided by Enumerable

• The “each” items of the collection must implement <=>

• Combined comparison operator. Returns 0 if first operand equals second, 1 if first operand is greater than the second and -1 if first operand is less than the second.


And NOW for the fun part!


Mixin MatchYou can add the Enumerable Module to your own classes!


Hokey Pokey!!


Each to her Own

• http://ruby-doc.org/core-2.0/Enumerable.html

• http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_modules.html


http://ruby-doc.org/core-2.0/Enumerable.html




http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_modules.html




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github.com/ggriffis

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@GingerGriffis


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