Most of my ruby notes live under my Rails notes or in my head.

Object

inspect

displays an object in some defined, human-readable form, showing instance variables.

Regex

• /asdf/
• %r{asdf}
• =~ for finding index of matches
• Regexp.quote(foo) escapes all special characters in the the string foo
• To interpolate a string into a regex, foo = "asdf", if "asdfsdf" =~ /#{Regexp.quote(foo)}/

File

• File.join(args) joins the arguements to make a file path based on File::SEPARATOR

Modules

Modules group together methods, classes, constants.

• Provide a namespace to prevent name clashes
• implement the mixin facility, eliminating the need for multiple inheritance
  • you can include a module in a class definition, then all module's instance methods are mixed in. So, mix-in modules effectively behave as superclasses.
  • Module methods can be defined like class methods.

include

include has nothing to do with files. It references a named module currently accessible. Does not copy functions into a class, creates a reference to them. With multiple classes including, they all point to the same thing.

For some class, you can use ruby's built in Comparable mixin, and def <=>(other) to define how to compare two objects.

Iterators and Enumerable Module

• need to def each: then include Enumerable module, which defines map, include?, find_all?
• need to def <=>(other): then max, min, sort are available

AutoLoad

autoload :MyLibrary, 'mylibrary' works like require 'mylibrary' but it only loads dependencies on the first time they're used rather than during the call itself. Symbol is the classname assigned, ruby file to be loaded is found using the relative file directory location.

Useful Array Methods

• Array#Permutation
• Array#Combination