Rails：渴望获取关联，而不是查找

Question

I've got three nested models: user has many plates and plate has many fruits . I also have a current_user helper method that runs in the before filter to provide authentication. So when I get to my controller, I already have my user object. How can I load all the user's plates and fruits at once?

In other words, I'd like to do something like:

@plates = current_user.plates(include: :fruits)

How can I achieve this?

I'm using Rails 3.1.3.

Answer 1

You will probably want to use the provided #includes method on your relation. DO NOT USE #all unless you intend to immediately work through the records, it will immediately defeat many forms of caching.

Perhaps something like: @plates = current_user.plates.includes(:fruits)

Unfortunately, there are portions of the Rails API that are not as well documented as they should be. I would recommend checking out the following resources if you have any further questions about the Rails query interface:

• Query Interface Guide
• ActiveRecord::Relation Walkthrough (screencast)

The query interface is possibly the most difficult part of the Rails stack to keep up with, especially with the changes made with Rails 3.0 and 3.1.

Answer 2

You can do

ActiveRecord::Associations::Preloader.new([current_user], :plates => :fruit).run

To eager load associations after current_user was loased. The second argument can be anything you would normally pass to includes : a symbol, an array of symbols, a hash etc

Answer 3

@plates = current_user.plates.all(:include => :fruits)

应该这样做。