Proc version of menu selection

menus.rb

#
# Not saying it's a good idea, but it's interesting.
#

# A Proc is just something you can call, with arguments.

p = Proc.new { |wat| puts wat }
p.call "ohai"
# => "ohai"

# The argument to Hash.new is what's returned if a key isn't found.
# This will return a callable proc that returns the string "Menu.last".
menus = Hash.new(Proc.new { |p| "Menu.last" })

# The "items" and "categories" controllers behave the same way.
# This Proc uses its parameter, the params hash.
itemcats = Proc.new { |p| "Menu.find(#{p[:menu_id]})" }
menus["items"] = menus["categories"] = itemcats

# This returns a callable proc that checks for the :id key in the hash.
menus["menus"] = Proc.new { |p| p[:id] ? "Menu.find(#{p[:id]})" : "Menu.first" }

# Should get the default.
puts menus["bogus_controller"]

# Need a menu_id. Although you should decide what to do if there isn't one.
params = { :menu_id => 42 }
puts menus["items"].call(params)
puts menus["categories"].call(params)

# The "menus" controller has two paths, if there's an id...
params = { :id => 69 }
puts menus["menus"].call(params)

#... and if there isn't.
params = {}
puts menus["menus"].call(params)