README.md

EG - Prototype based objects for Ruby

INSTALL | USAGE

What is EG

EG is a small gem that lets you create objects based on a prototype instead of a class definition. Eg is useful for creating singletons, mockups, service or factory objects, or simply for writing simple scripts without resorting to the class MyClass; ...; end; my_object = MyClass.new dance.

require 'eg'

greeter = EG.(
  greet: -> (name) { puts "Hello, #{name}!" }
)

greeter.greet('world')

Installing EG

$ gem install eg

Or add it to your Gemfile, you know the drill.

Using EG

The EG module is a callable that accepts a single hash argument containing method prototypes and constant definitions. You can define methods, constants and instance variables:

o = EG.(
  foo:    -> { @bar },
  '@bar': :baz,
  VALUE:  42
)

o.foo    #=> :baz
o::VALUE #=> 42

Defining methods

Any prototype key that does not begin with an upper-case letter or @ is considered a method. If the value is a proc or responds to #to_proc, it will be used as the method body. Otherwise, EG will wrap the value in a proc that returns it:

o = EG.(
  foo: -> { :bar },
  bar: :baz
)

o.foo #=> :bar
o.bar #=> :baz

Defining constants

Constants are defined using keys that begin with an upper-case letter:

o = EG.(
  AnswerToEverything: 42
)

o::AnswerToEverything #=> 42

Care should be taken to always qualify constants when accessing them from prototype methods by prefixing them with self:::

o = EG.(
  A: 1,
  a: ->(x) { self::A + x }
)

o.a(2) #=> 3

Defining instance variables

Instance variables are defined using keys that begin with an @:

o = EG.(
  '@count': 0,
  incr: -> { @count += 1 }
)

o.incr #=> 1
o.incr #=> 2