suppressing NoMethodError when receiver is nil, within a block

Often in rails you'll do things like

<%= @post.author.name %>

but it may be that you have no post, or the post has no author, and even if that's ok, the above would raise. I came up with a solution that lets you do the following:

<%= ifnil("no author"){ @post.author.name } %>

If at any point the receiver is nil (either @post or #author), execution of the block is stopped and the default value is returned ("no author" in this case, but defaults to nil)

NoMethodError is still raised if you send an invalid message to a non-nil receiver.

Here's the code for ifnil

def ifnil(value=nil)
  yield
  rescue NoMethodError
  raise unless $!.message =~ /:NilClass$/
  value
end

Typo current error

NoMethodError in Admin/content#new 
undefined method `text_filter=' for #
app/controllers/admin/content_controller.rb:24:in `new'
Show framework trace 
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.11.1/lib/active_record/base.rb:1200:in `method_missing'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/base.rb:756:in `send'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/base.rb:756:in `perform_action_without_filters'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/filters.rb:295:in `perform_action_without_benchmark'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/benchmarking.rb:41:in `perform_action_without_rescue'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/benchmarking.rb:41:in `measure'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/benchmarking.rb:41:in `perform_action_without_rescue'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/rescue.rb:80:in `perform_action'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/base.rb:356:in `send'
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.9.1/lib/action_controller/base.rb:356:in `process'
/usr/local/lib/ruby/gems/1.8/gems/rails-0.13.1/lib/dispatcher.rb:32:in `dispatch'
/home/rsimplicio/web/public/typo/dispatch.fcgi:20
/home/rsimplicio/web/public/typo/dispatch.fcgi:18:in `each_cgi'
/usr/local/lib/ruby/gems/1.8/gems/fcgi-0.8.6.1/./fcgi.rb:597:in `each'
/usr/local/lib/ruby/gems/1.8/gems/fcgi-0.8.6.1/./fcgi.rb:597:in `each_cgi'
/home/rsimplicio/web/public/typo/dispatch.fcgi:18
    
Request
Parameters: None

Show session dump

--- 
:user: !ruby/object:User 
  attributes: 
    name: Robert
    id: "1"
    password: 
    login: Robert
    email: 
:return_to: 
flash: !ruby/hash:ActionController::Flash::FlashHash {}
Response
Headers: {"cookie"=>[], "Cache-Control"=>"no-cache"}

Howto Send Email When Rails Throws An Exception

Add the following to your application.rb:

  protected  

  def log_error(exception) 
    super(exception)

    begin
      ErrorMailer.deliver_snapshot(
        exception, 
        clean_backtrace(exception), 
        @session.instance_variable_get("@data"), 
        @params, 
        @request.env)
    rescue => e
      logger.error(e)
    end
  end

Taken from http://wiki.rubyonrails.com/rails/show/HowtoSendEmailWhenRailsThrowsAnException