Update a model instance's field upon creating it? (Rails)
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I have 3 models/tables: User, Task, and TaskInstance. The Task table is like a master list of tasks, not coupled to any particular user, whereas the TaskInstance table contains records that indicate a user's completion of a particular task. In other words, a TaskInstance has a User id, a Task id, and a status boolean. A User has many TaskInstances. Users do not share TaskInstances, they each have their own collection.

What I would like to happen when a user first signs up for an account on the website is for the `User.task_instances` field to be populated with a new TaskInstance for every Task that exists in the master list.

From what I've read, I think I have to do this using `before_create`, because that should update the User before it gets saved for the first time. So far I have:

    class User < ActiveRecord::Base

        has_many :task_instances    

        before_create :populate_task_instances
    
        private

            def populate_task_instances
                #something here
            end
    end

So far I'm unsure of what goes in the `populate_task_instances` method. How do I loop through every record in the Task table and create a TaskInstance for each, and then ensure that the collection of TaskInstances gets saved to the User's `task_instances` field?

I understand this is pretty trivial but this is my first foray into Rails.