From: Rob Biedenharn <Rob@...>
Date: 2010-03-31T10:27:18+09:00
Subject: Re: why getting error for this code fragment

On Mar 30, 2010, at 8:27 PM, Amishera Amishera wrote:
>  5 class Movie_Info
>  6         attr_accessor :runtime, :language, :sound, :color
>  7         def to_str
> 38                 puts
> (runtime==nil?'nil':runtime)+'&&&'+(language==nil?'nil':language) 
> +'&&&'+(color==nil?'nil':color)+'&&&'+(sound==nil?'nil':sound)
> 39                 return str
> 40         end
> 41 end
>
> the statement at line 38 causes some error.
>
> ./util.rb:38: syntax error, unexpected tSTRING_BEG, expecting kDO or  
> '{'
> or '(' (SyntaxError)
>                puts
> (runtime==nil?'nil':runtime)+'&&&'+(language==nil?'nil':language) 
> +'&&&'+(color==nil?'nil':color)+'&&&'+(sound==nil?'nil':sound)
> -- 
> Posted via http://www.ruby-forum.com/.
>


Try it like this:

  5 class Movie_Info
  6         attr_accessor :runtime, :language, :sound, :color
  7         def to_str
38                 puts (runtime==nil ? 'nil' : runtime)+'&&&'+ 
(language==nil ? 'nil' : language)+'&&&'+(color==nil ? 'nil' : color) 
+'&&&'+(sound==nil ? 'nil' : sound)
39                 return str
40         end
41 end

It might be that ?' is being parsed as a character literal or it might  
be that :runtime is being parsed as a symbol. It's hard to tell  
because it seems to be missing lines 8..37. But in any case, I think  
that you are really trying for something like these. All three of  
these should give you the same result. In your original, you never  
create a str variable.  The puts will send output to $stdout, but not  
return anything except nil.

Also, the to_str is used when the object should act like a String.  
Compare that with to_s which typically returns a representation of the  
object as a string (often a more human-readable version that the  
default from Object#to_s).


class Movie_Info
   attr_accessor :runtime, :language, :sound, :color
   def to_str
     str = self.runtime || 'nil'
     str << '&&&' << (self.language || 'nil')
     str << '&&&' << (self.color || 'nil')
     str << '&&&' << (self.sound || 'nil')
     str
   end
end

class Movie_Info
   attr_accessor :runtime, :language, :sound, :color
   def to_str
     [ :runtime, :language, :color, :sound ].map do |field|
       self.send(field) || 'nil'
     end.join('&&&')
   end
end

class Movie_Info
   attr_accessor :runtime, :language, :sound, :color
   def to_str
     [ :runtime, :language, :color, :sound ].map do |field|
       instance_variable_get("@#{field}") || 'nil'
     end.join('&&&')
   end
end

-Rob
Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com