5 ms·

AbstractQueryFactoryFactories and alias_method_chain: The Ruby Way

42 points by wycats 17y ago

naz 17y ago
Good writeup but it could have been more useful if he showed the equivalent Java code.
- jdminhbg 17y ago
  The equivalent Java code is in the original post he's responding to.
  - pvg 17y ago
    It's Scala code.
duairc 17y ago
I've always thought that alias_method was a pretty silly way to solve the problem of defining a new method in terms of an existing method with the same name. alias_method is definitely "simpler", but I think the way it actually destructively creates a method in a class is a bit ugly. I don't know what "AbstractQueryFactoryFactories" are, but the name makes me want to stay pretty far away from them. These monkey patches constitute my solution to the problem: class UnboundMethod def origin owner.instance_method(name) end end class Proc def to_method(object, method) me = self object.class.class_eval do current = instance_method(method).origin rescue nil mine = current.owner == self rescue false define_method(method, &me) result = instance_method(method) mine ? define_method(method, current) : remove_method(method) result end.bind(object) end end class Module def redefine(method, &code) original = instance_method(method).origin define_method(method) do |*args, &block| code.to_method(self, method).(original.bind(self), *args, &block) end end end You use this as follows: Fixnum.redefine(:+) do |old_plus, other| if self == 2 and other == 2 5 else old_plus.(other) end end >> 2 + 2 => 5 >> 2 + 3 => 5 >> 2 + 1 => 3 I'll admit that its implementation is pretty horrible, but I think the interface is much nicer: you pass in a function which specifies your new function in terms of the old one, which is always passed as the first argument.
- jherdman 17y ago
  You're actually reimplementing some parts of Ruby that already exist: http://ruby-doc.org/core-1.8.7/classes/UnboundMethod.html http://ruby-doc.org/core-1.8.7/classes/UnboundMethod.html
  - duairc 17y ago
    Sorry, I'm not sure what you mean. What did I implement that already exists? The only method I added to UnboundMethod was origin, and I don't see a method on that page that does that.
    - jherdman 17y ago
      Err... apologies. I thought you were unaware of the UnboundMethod class.
deleted 17y ago
[deleted]
hypermatt 17y ago
I'm glad someone responded to the original post, after so many years of java, I can't really say I ever enjoyed factories they always seemed to solve a problem that was a weakness in the language itself.
- technomancy 17y ago
  I'm surprised anyone bothered; the original post was so very obviously troll bait. People who've been in the Ruby community as long as Yehuda should know better.

42 points by wycats 17y ago

naz 17y ago

Good writeup but it could have been more useful if he showed the equivalent Java code.

jdminhbg 17y ago
The equivalent Java code is in the original post he's responding to.
- pvg 17y ago
  It's Scala code.

duairc 17y ago

I've always thought that alias_method was a pretty silly way to solve the problem of defining a new method in terms of an existing method with the same name. alias_method is definitely "simpler", but I think the way it actually destructively creates a method in a class is a bit ugly. I don't know what "AbstractQueryFactoryFactories" are, but the name makes me want to stay pretty far away from them. These monkey patches constitute my solution to the problem: class UnboundMethod def origin owner.instance_method(name) end end class Proc def to_method(object, method) me = self object.class.class_eval do current = instance_method(method).origin rescue nil mine = current.owner == self rescue false define_method(method, &me) result = instance_method(method) mine ? define_method(method, current) : remove_method(method) result end.bind(object) end end class Module def redefine(method, &code) original = instance_method(method).origin define_method(method) do |*args, &block| code.to_method(self, method).(original.bind(self), *args, &block) end end end You use this as follows: Fixnum.redefine(:+) do |old_plus, other| if self == 2 and other == 2 5 else old_plus.(other) end end >> 2 + 2 => 5 >> 2 + 3 => 5 >> 2 + 1 => 3 I'll admit that its implementation is pretty horrible, but I think the interface is much nicer: you pass in a function which specifies your new function in terms of the old one, which is always passed as the first argument.

jherdman 17y ago
You're actually reimplementing some parts of Ruby that already exist: http://ruby-doc.org/core-1.8.7/classes/UnboundMethod.html http://ruby-doc.org/core-1.8.7/classes/UnboundMethod.html
- duairc 17y ago
  Sorry, I'm not sure what you mean. What did I implement that already exists? The only method I added to UnboundMethod was origin, and I don't see a method on that page that does that.
  - jherdman 17y ago
    Err... apologies. I thought you were unaware of the UnboundMethod class.

deleted 17y ago

[deleted]

hypermatt 17y ago

I'm glad someone responded to the original post, after so many years of java, I can't really say I ever enjoyed factories they always seemed to solve a problem that was a weakness in the language itself.

technomancy 17y ago
I'm surprised anyone bothered; the original post was so very obviously troll bait. People who've been in the Ruby community as long as Yehuda should know better.