hook methods

class A
    def a
        p :_a
    end
    def b
        p :_b
    end
end
A.class_eval {
    public_instance_methods(false).each { |name|
        old = instance_method(name)
        define_method(name) { |*a, &b|
            p __callee__
            old.bind(self).call(*a, &b)
        }
    }
}
A.new.a