In a screen cast on Exporting CSV from a rails app, Ryan Bates presented the following simple code.
I'm trying to figure out how the class method Product::to_csv actually gets invoked on line 5 of ProductController.rb, as it doesn't seem to follow the normal Ruby rules.
product.rb
1 class Product < ActiveRecord::Base
2 def self.to_csv(options = {})
3 ...
4 end
5 end
products_controller.rb
1 class ProductsController < ApplicationController
2 def index
3 @products = Product.order(:name)
4 respond_to do |format|
5 format.csv { send_data @products.to_csv }
6 ...
7 end
8 end
9 end
Since to_csv is a class method, I'd expect the invocation to look like Product::to_csv().
According to the documentation, @products is an instance of ActiveRecord::Relation. Why do messages sent to an instance of ActiveRecord::Relation cause methods on the Product class object to get invoked? To make it even stranger, renaming to_csv to some arbitrary name in both the the sender and receiver leads to NoMethodError, so maybe there is some magic afoot based on names that begin with to_?
Am I missing something obvious? Any clarification would be greatly appreciated.
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