From: Pit Capitain <pit@...>
Date: 2005-12-08T01:11:39+09:00
Subject: Re: Syntax checker?

William E. Rubin schrieb:
> Ruby doesn't seem to check for class names, function names, and so
> forth until it actually hits a line that tries to use such a thing.  Is
> there a way to get it to check up front, without having to run the
> script through every possible line of code?
> 
> I understand that this is not strictly "syntax" checking, and that Ruby
> does actually do a "syntax" check.  So I mean some other term, more
> along the lines of what a traditional compiler will do (minus the
> actual compilation).

Hi William,

if you call the ruby interpreter with the -c command line option, then 
it performs a syntax check:

   C:\tmp>ruby -c r.rb
   Syntax OK

(http://www.ruby-doc.org/docs/ProgrammingRuby/html/rubyworld.html#UA)

On the other hand, if you want to syntactically check for valid class 
names, then you're out of luck. Ruby is too dynamic. Look at this little 
script:

   C:\tmp>type r.rb

   print "enter class name: "
   name = gets.chomp
   Object.const_set name, Class.new
   p X.new

This script prompts the user for a classname and then creates a new 
class under that name. It then tries to create an instance of class X. 
You can't check whether "X" is a valid class name without actually 
running the code:

   C:\tmp>ruby r.rb
   enter class name: X
   #<X:0x2b31708>

   C:\tmp>ruby r.rb
   enter class name: Y
   C:/tmp/r.rb:5: uninitialized constant X (NameError)

I'm not sure the Ruby IDEs can give you more hints about misspelled 
names. The best way for me is simply doing Test Driven Development.

Regards,
Pit