From: "Mauricio Fernández" <batsman.geo@...>
Date: 2003-03-21T01:41:05+09:00
Subject: Re: class level Exception handling

On Fri, Mar 21, 2003 at 01:08:30AM +0900, Xiangrong Fang wrote:
> Hi
> 
> Could anyone teach me about the following?
> 
> 1. in a File.open do ... end block, if I call break or return to exit
> the block, will the file be closed?

I guess yes, as it uses rb_ensure.
 
> 2. Is there a way to write a class-level exception handler? See the
> following:
> 
> class A
>      def method 1
>           begin
>              ...
>           rescue
>           end
>      end
>      def method 2
>           begin
>              ...
>           rescue
>           end
>      end
> end
> 
> in the above code, I do a lot of TCP Socket related work in method1
> method2 etc. I would like to return false for all these methods if
> there's any error, can I do better than use a begin/rescue/end for every
> of them?

batsman@tux-chan:/tmp$ expand -t2 < p.rb

module WrapMethod
  def __block__(meth)
    @blocks[meth]
  end
  def wrap(*args, &block)
    @blocks ||= {}
    args.each do |meth|
      alias_method "__#{meth.to_s}__".intern, meth
      @blocks[meth] = block
      module_eval <<-EOF
      def #{meth.to_s}(*args,&b)
        begin
          return __#{meth.to_s}__(*args,&b)
        rescue Exception
          return self.class.__block__(:#{meth.to_s}).call
        end
      end
      EOF
    end
  end
end

class A
  extend WrapMethod
  def foo; raise "BAD THING"; end
  def bar; raise "and another!"; end
  def baz; "GOOD"; end

  wrap :foo, :bar, :baz do
    puts "Got #{$!.inspect}"
    false
  end
end


a = A.new
puts a.foo, a.bar, a.baz
batsman@tux-chan:/tmp$ ruby p.rb
Got #<RuntimeError: BAD THING>
Got #<RuntimeError: and another!>
false
false
GOOD

-- 
 _           _                             
| |__   __ _| |_ ___ _ __ ___   __ _ _ __  
| '_ \ / _` | __/ __| '_ ` _ \ / _` | '_ \ 
| |_) | (_| | |_\__ \ | | | | | (_| | | | |
|_.__/ \__,_|\__|___/_| |_| |_|\__,_|_| |_|
	Running Debian GNU/Linux Sid (unstable)
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	--Larry Wall