Using alias_method before function definition

Ruby
1

Hi guys, I’m having problems with using alias_method. When i run this
code, I’m getting undefined method shout' for class Person’
(NameError) since I’m using alias_method on a function that is probably
not defined yet. The example would work if I put the profile method
after the method name, but is there a cleaner solution to make this
work? This post (Problems with alias_method - Ruby - Ruby-Forum) seem to solve
this problem using “method_added” callback but i hope i could use a
different approach

module SimpleProfiler
def profile(*methods)
methods.each do |method|
send :alias_method, “orig_#{method}”, method

  define_method method do |name|
    before = Time.now
    send "orig_#{method}", name
    after = Time.now
    puts sprintf("%s: %.4fs", method, after - before)
  end
end

end
end

class Person
extend SimpleProfiler
profile :shout

def shout(name)
sleep(1)
puts name
end
end

p = Person.new
p.shout(“reg”)

2

Oops, correction:

define_method method do |name|
before = Time.now
send “orig_#{method}”, name
after = Time.now
puts sprintf("%s: %.4fs", method, after - before)
end

should be

define_method method do |*args|
before = Time.now
send “orig_#{method}”, *args
after = Time.now
puts sprintf("%s: %.4fs", method, after - before)
end

3

hmm, maybe i should use something else other than alias_method. or i’ll
probably just stick with method_added callback

4

Reginald T. wrote in post #1024307:

The example would work if I put the profile method
after the method name, but is there a cleaner solution to make this
work?

I don’t think so. The trouble is, alias_method acts on the version of
the method as it was defined at that time. So you could define a dummy
method first, and copy it with alias_method, but when you redefine it
the alias would still point to the first one.

def foo
puts “Version 1”
end

alias :bar :foo

def foo
puts “Version 2”
end

foo # prints “Version 2”
bar # prints “Version 1”

HTH,

Brian.