Creating form for an object which has an association - ruby-on-rails

Question

I have two models: project and todo. Project has many todos.
So I wanna create a form, where I select project category from the combobox and then I add a todo to it.
For instance:
I have following categories: family, work, study.
In form in the combobox I select 'study', and then in textfield I spell a todo like 'make homework for monday' and press submit button.
project.rb
class Project < ActiveRecord::Base
has_many :todos
end
todo.rb
class Todo < ActiveRecord::Base
belongs_to :project
end
my data schema:
create_table "projects", force: :cascade do |t|
t.string "title"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "todos", force: :cascade do |t|
t.string "text"
t.boolean "isCompleted"
t.integer "project_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
_form.html.erb
<%= form_for #project do |f| %>
<div class="form_control">
<%= f.select :title, options_for_select([["Work", "w"],
["Family", "f"],
["Study", "f"],
["TheRest", "t"]]) %>
</div>
<div class="form_control">
*** HERE I NEED TO FIGURE OUT HOW TO ADD SOME DATA TO todo.text ***
</div>
<div class="form_control">
<%= f.submit 'Add' %>
</div>
<% end %>
this is how I show all the projects with their todos:
<% #projects.each do |project| %>
<h2> <%= project.title %> </h2>
<% project.todos.all.each do |todo| %>
<p><%= todo.text %> <%= check_box('tag', todo.__id__, {checked: todo.isCompleted}) %></p>
<% end %>
<% end %>
GitHub link : https://github.com/NanoBreaker/taskmanager

Answer 1

In your todo form, you could have a select box to choose the project the todo belongs to:
# todos/_todo_form.html.erb
<%= select_tag "project_id", options_for_select(Project.pluck(:title, :id)) %>
And in your todos_controller create action:
def create
#project = Project.find(params[:project_id])
#todo = #project.todos.new(todo_params)
if #todo.save
# success
else
# error
end
end
finally, permit the project_id in todo_params:
def todo_params
params.require(:todo).permit(:text, :project_id) # add any other attributes you want
end