From: Alex Young <alex@...>
Date: 2006-09-10T02:44:07+09:00
Subject: Re: Thousands of words on Ruby

James Edward Gray II wrote:
> On Sep 9, 2006, at 10:33 AM, Alex Young wrote:
> 
>> James Edward Gray II wrote:
>>> On Sep 9, 2006, at 9:41 AM, Alex Young wrote:
>>>> Ok, so it's a real bodge to try to rename a method before runtime.  
>>>> What happens if we annotate the method to be renamed the next time 
>>>> it's run?  We could run the script in question under an environment 
>>>> not totally unlike xmp.  The first thing it would do is alter the 
>>>> source file according to the annotation.  It would then add an 
>>>> appropriate method_missing to Object to do a rename in the original 
>>>> source file whenever the method was called, and then load() the file.
>>> And what happens if the execution never calls the given method, for 
>>> whatever reason, or only reaches some of the places it is used?
>> That's why you run your test suite through it.  You do have 100% line 
>> coverage, right?  :-)
> 
> Well it's a clever idea.  Show us the prototype.  ;)

Well, you asked for it :-)  The usual provisos for prototype code apply:


$ cat rename_method.rb
$obj_replacement_table = {}
class Object
   def method_missing(sym, *args, &block)
     if $obj_replacement_table.has_key? sym.to_s
       filename, line_num = caller[0].split(':')[0,2]
       l = line_num.to_i - 1
       line_arr = File.readlines(filename)
       line_arr[l] = line_arr[l].sub(sym.to_s, 
$obj_replacement_table[sym.to_s])
       File.open(filename, 'wb'){|f| f.write line_arr}
       self.send($obj_replacement_table[sym.to_s].to_sym, *args, &block)
     end
   end
end

def process_file(filename)
   line_arr = File.readlines(filename)
   line_arr.each_with_index do |line,i|
     if line.chomp =~ /(\s+)def (\w+)(.*)#\s*becomes\s+(\w+)/
       line_arr[i] = "#{$1}def #{$4}#{$3}# was #{$2}\n"
       $obj_replacement_table[$2] = $4
     end
   end
   File.open(filename, 'wb'){|f| f.write line_arr }
end

process_file(ARGV[0])
load(ARGV[0])


$ cat subject.rb
class TestClass
   def my_method(foo) # becomes my_new_method
     puts foo
   end
end

def meth_calling_renamed(t)
   t.my_method('Ok2')
end

t = TestClass.new
t.my_method('Ok1')
meth_calling_renamed(t)


$ ruby rename_method.rb subject.rb
Ok1
Ok2

$ cat subject.rb
class TestClass
   def my_new_method(foo) # was my_method
     puts foo
   end
end

def meth_calling_renamed(t)
   t.my_new_method('Ok2')
end

t = TestClass.new
t.my_new_method('Ok1')
meth_calling_renamed(t)


There's a *lot* of scope for improvement in there, obviously, but that's 
the general idea.

-- 
Alex