Module: Arrow::Injectable

Defined in:
lib/arrow/mixins.rb

Overview

Adds dependency-injection bejavior to a class. Classes which are Injectable are loadable by name, making it easier to refer to them from a configuration file or other symbolic source. Instead of classes explicitly referring to one another to satisfy their associations, these dependencies can be “injected” at runtime.

Some references for the Dependency Injection pattern:

* http://www.martinfowler.com/articles/injection.html
* http://en.wikipedia.org/wiki/Dependency_injection

Usage

# in myclass.rb require ‘arrow/mixins’

class MyClass

include Arrow::Injectable

end

# somewhere else myclass = Arrow::Injectable.load_class( “myclass” )

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.derivatives ⇒ Object 



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# File 'lib/arrow/mixins.rb', line 340

def self::derivatives; @derivatives; end

.extend_object(obj) ⇒ Object

Make the given object (which must be a Class) injectable.

Raises:

  • (ArgumentError) 


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# File 'lib/arrow/mixins.rb', line 343

def self::extend_object( obj )
  raise ArgumentError, "can't make a #{obj.class} Injectable" unless
    obj.is_a?( Class )
  super
  @derivatives[ obj.name ] = obj
end

.included(mod) ⇒ Object

Mixin hook: extend including classes



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# File 'lib/arrow/mixins.rb', line 352

def self::included( mod )
  Arrow::Logger[self].debug "%s included Injectable" % [ mod.name ]
  mod.extend( self )
  super
end

.load_class(classname) ⇒ Object

Return the Class object for the given derivative classname, attempting to load it if it hasn’t been already.



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# File 'lib/arrow/mixins.rb', line 361

def self::load_class( classname )
  Arrow::Logger[self].debug "Loading injectable class '#{classname}'"

  unless Arrow::Injectable.derivatives.include?( classname )
    modname = classname.downcase.gsub( /::/, '/' )
    Arrow::Logger[self].debug "Class not loaded yet. Trying to " +
      "load it from #{modname}"
    require modname or
      raise "%s didn't register with Injectable for some reason" % [ classname ]
    Arrow::Logger[self].debug "Loaded injectable class %s (%d classes loaded)" %
      [ classname, Arrow::Injectable.derivatives.length ]
  end

  Arrow::Injectable.derivatives[ classname ]
end

Instance Method Details

#inherited(klass) ⇒ Object

Classes which inherit from Injectable classes should be Injectable, too.



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# File 'lib/arrow/mixins.rb', line 384

def inherited( klass )
  Arrow::Logger[self].debug "making %s Injectable" % [ klass.name ]
  klass.extend( Arrow::Injectable )
  super
end