How can I dynamically define an alias method for a class method?

ruby

Solution

So just learned that this will do the trick:

module Calculator
  def memoize
    define_singleton_method(name, method(name))
  end
end

Then when Calculator gets included in Product it will define the singleton method as I needed. I still don't know why alias_method needs to only work on instance methods.. and I don't know why class_eval or instance_eval didn't solve the problem.. but at least I have a solution..

Problem

I have a module lets call "Calculator" that I want to include in a class "Product". Calculator will extend "Product" which will copy the class methods onto Product. One of these class methods is "memoize". The idea being that I can do something like this: ``` module Calculator def self.extended(base) base.memoize :foo_bar end end ``` With the purpose of memoizing the method (specifically a class method) :foo_bar. Inside of memoize I call the method "alias_method" which attempts to alias a class method to a different name (here :foo_bar). This fails. Memoize looks something like: ``` module Calculator (the extended module) def memoize(name) alias_method "memoized_#{name}", name end end ``` When this is called via memoize :foo_bar, the alias_method line kicks an error saying Product has no method "name".. my understanding is this is because alias_method will attempt to alias instance methods not class methods.. (I don't know why but ok no big deal).. I can reopen the eigenclass like so ``` module Calculator def memoize(name) class << self alias_method "memoized_#{name}", name end end end ``` This would work but name is not available to the scope of the class << self definition. People have mentioned using self.class_eval and self.instance_eval but neither of these seem to work.. I'd like my cake and eat it too.. how can I keep alias_method dynamic but use it on class_methods?

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