This gem is exceptionally simple but also very handy. Let's say you are working in ActiveRecord and you have loaded a collection of objects in a query. You now want to preload associations for these already retrieved objects. This allows you to do that.
The usage of this is very straightforward:
@users = User.all @users.preload(:posts)
This will eager load all posts for each user even after the initial find query has taken place. You can also use this to preload associations for a member as well:
@user = User.first @user.preload(:posts)
Why not just do?
Good question. In most cases this is the better option. This code is for when that approach is not available.