On Mon, 24 Nov 2008, Matthew M. wrote:
Can anyone explain exactly what happens when the interpreter interprets
attr_reader and its kin?
E.G. where is the method located (in which module, class) and what does
it do with the symbols in order to expand the method call into an
instance method of the calling class object?
attr_reader and friends are private instance methods of the class
=> [“attr_accessor”, “attr_writer”, “attr_reader”, “attr”]
which means that as long as self is an instance of Module or one of
its subclasses, those methods can be called. The Class class is a
subclass of Module, so instances of Class can execute those methods
too. That’s what’s happening when you do:
As for what it does: see Greg’s Ruby implementation, and also the
original C code which is in eval.c (look for the definition of
rb_attr). It basically calls rb_define_method, which is a general
method for adding methods to classes.
I used implementing attr_* as a metaprogramming exercise in a Ruby
course I taught last week, and it was very instructive. Amazing what
you can do in Ruby, without even getting terribly convoluted or