What are some good examples of Mixins and or Traits?

Question

I was reading up on Ruby, and learned about its mixins pattern, but couldn't think of many useful mixin functionality (because I'm not used to thinking that way most likely). So I was wondering what would be good examples of useful Mixin functionality?

Thanks

Edit: A bit of background. I'm Coming from C++, and other Object languages, but my doubt here is that Ruby says it's not inheriting mixins, but I keep seeing mixins as Multiple inheritance, so I fear I'm trying to categorize them too soon into my comfort zone, and not really grok what a mixin is.

Answer 1

Well the usual example I think is Persistence

module Persistence
    def load sFileName
        puts "load code to read #{sFileName} contents into my_data"
    end

    def save sFileName
        puts "Uber code to persist #{@my_data} to #{sFileName}"
    end

end

class BrandNewClass
    include Persistence
    attr :my_data
    
    def data=(someData)
        @my_data = someData
    end
end

b = BrandNewClass.new
b.data = "My pwd"
b.save "MyFile.secret"
b.load "MyFile.secret"

Imagine the module is written by a Ruby ninja, which persists the state of your class to a file.
Now suppose I write a brand new class, I can reuse the functionality of persistence by mixing it in by saying include ModuleILike. You can even include modules at runtime. I get load and save methods for free by just mixing it in. These methods are just like the ones that you wrote yourself for your class. Code/Behavior/Functionality-reuse without inheritance!

So what you're doing is including methods to the method table for your class (not literally correct but close).