CODEWITHSUNDEEP
rubypointersmethods
Alex Poca
Alex Poca

Reputation: 2566

Ruby, pointer to method

Ruby toddler here (3 days playing with Ruby, probably my terminology is yet imprecise).

For study reason I would like to modify the following code to accept ticket.request("triple",10) (or equivalent syntax) in the second last line.

Is it possible (without heavily changing ticket.request)? 

ticket = Object.new

def ticket.price
  return 3.5
end

def ticket.triple(c)
  return 3*c
end

# direct call
puts ticket.triple(10)   # ===> 30

# pointer to method
pt = ticket.method(:triple)  
puts pt.call(10)         # ===> 30


def ticket.request(request)    # <=== should it be modified?
  if self.respond_to?(request)
    self.__send__(request)
  end # nil otherwise
end

puts [
   ticket.price,            # direct ===> 3.5
   ticket.request("price"), # safe   ===> 3.5
   ticket.request("name")   # it does not exist ===> nil
 # ticket.request("triple", 10)   <========================= syntax ????
]

Upvotes: 0

Views: 104

Answers (2)

Marek Lipka
Marek Lipka

Reputation: 51151

So, basically you need ticket.request method to take also arguments you want to be passed to subsequent method call? It is possible, if so:

def ticket.request(request, *args)
  if respond_to?(request)
    send(request, *args)
  end
end
puts [
  ticket.price,            # direct ===> 3.5
  ticket.request("price"), # safe   ===> 3.5
  ticket.request("name")   # it does not exist ===> nil
  ticket.request("triple", 10) 
]

*args in method definition works as "take the rest of arguments and store them in args array. In the method call it works in quite opposite way - as "take args array and make it an argument list passed into the method".

Note that I deleted redundant self keywords, as self is default receiver of the message. I also used send method, as it's used more commonly.

Upvotes: 1

spickermann
spickermann

Reputation: 106802

I would do something like this:

def ticket.request(request, *args)
  if self.respond_to?(request)
    self.__send__(request, *args)
  end
end

Upvotes: 1

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