Question

The code:

user = ... #pretend it has a value :)
instances = Array.new
Product.all.each do |product|
    productInstance = ProductInstance.new
    productInstance.user = user
    productInstance.product = product
    instances.push(productInstance)
end

Product and ProductInstance are both Rails models. Is a for-each loop on Product.all going to be slow? Just wondering if there is a better way of doing this…

Answer 1

Somthing like this should work.

instances = Product.all.map do |product|
    productInstance = ProductInstance.new(:user => user,:product => product)
end

or even

instances = Product.all.map do |product|
    ProductInstance.new(:user => user,:product => product)
end

For Mass assignment restriction you can try something like

instances = Product.all.map do |product|
    ProductInstance.new {|instance| instance.user = user;instance.product = product}
end