Before_call, after_call, assert, ... why not?

Hi, I am a new Ruby addict, and I’ve a question/suggestion (sorry…).
I will try to explain myself by an example.
I tried to add assertions possibility in ruby, but I think it’s not the
best way to put them hardly in method body : I want to
enable/disable/add/delete them easily. I thus added an assertion
collection in Class, but how to force methods to call them ? Redefine
send ? Doesn’t work, and I don’t think it’s a good way. In my mind,
a nice solution could be : every Proc can specify other Proc what will
be called before/after them.

some uses

class Truc
def my_method a, b
# here: before_call(name_of_proc, &the_proc)
before_call {|a,b| raise “not same class” unless a.class ==
b.class }
a + b

here: before_call(method, name_of_proc=gensym(“proc_”), &the_proc)

Truc.before_call :my_method, :a_name do |a,b|
raise “a > b” if a > b

assert would be a shortcut for precious examples

Truc.assert :my_method, :name_of_assert, “message” do |a,b|

others uses

name not needed ?

Machin.after_call(:read_a_file){@file.close if}

Are Proc/before/after same binding ?

some_proc.before.each {|proc| …}

Is it envisageable ? (sorry if there is an discussion on this subject