```ruby
# Add a callback - to be executed before each request in development,
# and at startup in production - to patch existing app classes.
# Doing so in init/environment.rb wouldn't work in development, since
# classes are reloaded, but initialization is not run each time.
# See http://stackoverflow.com/questions/7072758/plugin-not-reloading-in-development-mode
#
Rails.configuration.to_prepare do

  # Example of adding a default text to each message
  # OutgoingMessage.class_eval do
  #   # Add intro paragraph to new request template
  #   def default_letter
  #     return nil if self.message_type == 'followup'
  #     "If you uncomment this line, this text will appear as default text in every message"
  #   end
  # end
end
```

Update model patch example to include the default_letter param override
user
```ruby
# Add a callback - to be executed before each request in development,
# and at startup in production - to patch existing app classes.
# Doing so in init/environment.rb wouldn't work in development, since
# classes are reloaded, but initialization is not run each time.
# See http://stackoverflow.com/questions/7072758/plugin-not-reloading-in-development-mode
#
Rails.configuration.to_prepare do

  # Example of adding a default text to each message
  # OutgoingMessage.class_eval do
  #   # Add intro paragraph to new request template
  #   def default_letter
  #     # this line allows the default_letter text added by this
  #     # method to be replaced by the value supplied by the API
  #     # e.g. http://demo.alaveteli.org/new/tgq?default_letter=this+is+a+test
  #     return @default_letter if @default_letter
  #     return nil if self.message_type == 'followup'
  #     "If you uncomment this line, this text will appear as default text in every message"
  #   end
  # end
end
```
assistant