sql - Adding a column Migration with a default value in ruby on rails -

i using sqlite3 , following work:

class addnametogoal < activerecord::migration   def change     add_column :goals, :goal_name, :text, default: goal.exercise.name   end end 

or maybe makes more sense i'm trying do:

add_column :goals, :gname, :text, default: goal.find(row_id).exercise.name 

how above work.

i doubt work that's want.

specifically, user associated exercise through exercise_id column.

belongs_to :user belongs_to :exercise has_many :workouts, dependent: :destroy 

(this model goal)...

i user able choose own name goal can give them hint name goal after exercise's name , if choose leave blank default exercise's name. more importantly must happen on sql side later when have collection drop down requires name of goal need name corresponds exercise.

<%= f.collection_select(:goal_id, @goals, :id,  :goal_name, :include_blank => "please select") %> 

the exercise model made in rails have id, name, other columns.

exercise model:

class exercise < activerecord::base     has_one :goal 

is there strategy possible.

another option me find strategy active record can do:

<%= f.collection_select(:goal_id, @goals, :id,  :goal_name, :include_blank => "please select") %> 

with (something else replace goal_name exercise.name goal.exercise.name , goal.id , show id.

doing when define column on table problematic. think doing upon creation, in model, how you'd want go.

you might check out the default_value_for gem , see if helps.