From: "Jan E." <lists@...>
Date: 2012-07-02T01:38:30+09:00
Subject: Re: Question on Learning Ruby the Hard Way

Hi,

For the next time, please *attach* the code rather than post it. The 
forum software inserts a line break after every 80 characters or so, 
which destroys the whole formatting.

It also seems you've silently left out several methods. Of course you 
can shorten the code, but then you should tell us. Well, for this 
particular example we can more or less guess which methods are missing 
and what they look like. But if this was a more complicated class, it 
would really be annoying to get an error message and having to figure 
out what's missing.

To the actual questions:

Michael Sung wrote in post #1066882:
> def play()
>     next_room = @start
>
>     while true
>       puts "\n--------"
>       room = method(next_room)
>       next_room = room.call()
>     end
>   end
>
>
> I can see that variable next_room is set to instance variable @start.
> But how does this "while" loop work?  I'm also not familiar with how
> "method" and "call" are both used here, as well as the : used in return
> (e.g. return :central_corridor) below.

The while loop is an endless loop. You probably know how a while loop 
works in general. In this case the condition is always true, so the loop 
will run forever.

However, it would have been better to use an explicit endless loop like 
Kernel#loop:

loop do
  # body
end

Calling "method" with a method name as a Symbol creates a Method object 
for this method. This object can then be passed around and called at any 
time (by calling the "call" method):

class A
  def f
    puts "f called"
  end
end

a = A.new
f = a.method(:f)  #create a Method object for method "f"
p f
f.call()          # call Method object (without arguments)

See
http://ruby-doc.org/core-1.9.3/Object.html#method-i-method
http://ruby-doc.org/core-1.9.3/Method.html

The Game class uses this to call methods dynamically: Every method like 
"central_corridor" or "laser_weapon_armory" returns the name of the 
method which should be called next (as a Symbol). This allows the user 
to control the flow of the game. For example, if he's in the central 
corridor and types in "shoot!", the "death" method will be called. If he 
types in "tell a joke", the "laser_weapon_armory" method will be called 
(he continues to the next room).

However, a better way to achieve this is by using Object#send. This 
method takes a method name as a Symbol together with optional arguments 
and then calls this method.

So you can replace

room = method(next_room)
next_room = room.call()

with

next_room = send next_room

See
http://ruby-doc.org/core-1.9.3/Object.html#method-i-send

It may also be a good idea to use "public_send" instead, which will only 
call public methods:

http://ruby-doc.org/core-1.9.3/Object.html#method-i-public_send

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