Rails 100% newb issue - send() method

Question

Could someone please help me to understand what the \'send()\' method listed below is used for? The code below, when I am reading it, makes no sense what purpose it\'s serving.<

Answer 1

send is used to pass a method (and arguments) to an object. It's really handy when you don't know in advance the name of the method, because it's represented as a mere string or symbol.

Ex: Performer.find(params[:performer_id]) is the same as Performer.send(:find, params[:performer_id])

Beware here because relying on params when using send could be dangerous: what if users pass destroy or delete? It would actually delete your object.

Answer 2

The send method is the equivalent of calling the given method on the object. So if the selected_track variable has a value of 1234, then @performer.send(selected_track) is the same as @performer.1234. Or, if selected_track is "a_whiter_shade_of_pale" then it's like calling @performer.a_whiter_shade_of_pale.

Presumably, then, the Performer class overrides method_missing such that you can call it with any track (name or ID, it isn't clear from the above), and it will interpret that as a search for that track within that performer's tracks.

Answer 3

The Ruby implementation for the send method, which is used to send a method message to an object, works like this:

class Car

  def start
    puts "vroom"
  end

  private

  def engine_temp
    puts "Just Right"
  end

end

@car = Car.new
@car.start # output: vroom
@car.send(:start) # output: vroom

That's the basics, an additional piece of important information is that send will allow you you send in messages to PRIVATE methods, not just public ones.

@car.engine_temp  # This doesn't work, it will raise an exception
@car.send(:engine_temp)  # output: Just Right

As for what your specific send call will do, more than likely there is a def method_missing in the Performer class that is setup to catch that and perform some action.

Hope this helps, good luck!