Ruby Overview

• Function parens are optional, like bash commands
• Repl is irb
• Command line doc lookup ri
• Dictionariess are called hashes.
• Backticks call a shell command, but don’t return the output, it is printed. Use system to capture it.

• Triple equals is less strict, like checking for range inclusion. But it’s not recommended to use over the methods.

• Use rbenv to install newer versions than the system.

Unique concepts

• Every method has an implicit block argument, which is called with yield
• Symbols, ie :something
  • Global unique objects instead of memory allocated strings.
  • Used for hash keys, function names, etc.
• Append opperator
  • string << "more characters"
  • Also for files, arrays, etc
• Delimited types
  • %w{some words} => array of the words.
  • There are others too, instead of w. Multiline string is one.
  • They can use almost any delimeter, if curly brace wont work.
  • <<~EOF ... EOF as a heredoc also works, simiar to %{ ... }
• String formatting
  • "string %s %d" % ["one", 1] Formatting with the percent sign, not terribly reccomended.
    • %p will inspect the object.
  • Interpolation with #{} is usually best.
  • Methods such as printf also exist
• irb uses the inspect method to print objects. However, interpolation uses to_s. to_str is only for things that are actually string represented.

• do ... end blocks are the same as curly braces (but different precedence for binding)
• if ... elsif ... else ... end
• loop do ... end is forever loop, like while true
• Both if and unless can be used as blocks. Both can be used at the end of a single line.
• If statements (and every other statement) returns a value, so can be assigned to a variable
• Last line in a block or method is implicitly returned.

• Variable names are important
  • Constants start with a capital letter. Likely to be all caps, but not required.
  • Globals start with $,
  • Object attributes start with @
  • Class attributes start with @@
• There is no public object attribute access, as if everything was private.
  • Objects can only have methods.
  • Accessors are easily defined by sybmol with attr_accessor, or attr for readonly.
• Special globals
  • $: search path
  • $" loaded modules
  • $0 running program
  • $* arguments
  • $! current exception
  • $@ backtrace of current exception

• Class inheritance with angle bracket. class Dog < Animal
• Type checking with is_a? method. Works for inherited types. But often checking for method existance (ie duck typing) is better, with respond_to?
• Mixins
  • Define a module, then include it in a class
  • class X; include SomeModule; end
  • Often, use this to extend a class that already exists.
• super is a refernce to the parent class' method, not a reference to self as the parent type.
• A method can be defined on a single object, without affecting other objects of the same class. def someObj.method ; :foobar ; end. This also works for adding class methods, but you could just define it in the class instead, by extending the class.
• You can create your own metaprogramming class methods, like attr, which output class code. Usually will eventually rely on eval, instance_eval, class_eval