Method Missing Best Practice
Method missing allows access to the object attributes, which are held in the @attributes hash, as though they were first-class methods.
If you call a method that doesn’t exist, Ruby will call the method_missing method, and pass the name of the method and any arguments you supplied, which means you can dynamically handle the method.
Here we go, for example, we have a messages table:
create_table "messages", :force => true do |t|
t.text "content"
t.boolean "is_read", :default => false
t.boolean "is_archived", :default => false
t.integer "post_id"
t.integer "user_id"
t.datetime "created_at"
t.datetime "updated_at"
end
As a general way, many people will define some following methods
class Message < ActiveRecord::Base
def is_read?
!!is_read
end
def is_archived?
!!is_archived
end
def mark_as_read!
update_attribute(:is_read, true)
end
def mark_as_unread!
update_attribute(:is_read, false)
end
def mark_as_archived!
update_attribute(:is_archived, true)
end
def mark_as_unarchived!
update_attributes(:is_archived, false)
end
end
Wow, this makes your code ugly, we can use method missing instead of these all methods
def method_missing(symbol, *args)
case symbol
when /^is_(un)?(.*)\?/
eval "#{$1 ? '!' : '!!'}is_#{$2}"
when /^mark_as_(un)?(.*)!/
update_attribute :"is_#{$2}", ($1 ? false : true)
else
super
end
end
When you call is_[string] method or mark_as_[string] method, as you can see, there is definitely no is_[string] or mark_as_[string] method, yet Rails is smart enough to call the method with the correct parameters, What we have done is to run a regular expression against the name of the method, and if it matches the pattern is_[string] or mark_as_[string] then it calls the method with the [string] part as the first parameter and the first argument as the second parameter. Pretty powerful, don't you think?