From: Morton Goldberg <m_goldberg@...>
Date: 2007-05-22T02:05:42+09:00
Subject: Re: Emergency help is needed

On May 20, 2007, at 2:25 PM, anoosh wrote:

> Hi all
> I have 2 questions?
> 1)What are the meaning of  symbols(:var) and Instance variables(@x)
> Ruby?(I know Java and C.If it is possible for you  tell me the
> synonyms in these languages,please)
>
> 2)How can I define my own exception handling in Ruby?

That's really three questions, but who's counting? :)

1a. There is nothing like Ruby symbols in Java or C. Perhaps the best  
way for you to think about symbols is as objects that can serve as  
unique identifiers. Their main advantage (over strings) is very quick  
equality comparison. This makes them good hash keys. They are never  
garbage collected, which means you probably shouldn't use them in a  
situation where you are making a lot of objects for temporary use.

1b. Instance variables are pretty much equivalent to the field  
members of a Java class.

2. I hope you mean "how do I handle exceptions in Ruby?" The Ruby  
equivalent of Java's

      try { ... } catch(<excpetion_name> e) { ... } finally { ... }

is

      begin
         ...
      rescue <excpetion_name> => e
         ...
      ensure
         ...
      end

You will really have to read up on this to use it effectively, but  
knowing the keywords will allow you to Google for further help.

Regards, Morton