can't write unknown attribute "parent_id", has_one and belongs_to - ruby-on-rails

Question

i'm using rails 4 and was wondering if anyone could find what's wrong in my code.
I have project model and I created a team model that has a belongs_to - has_one relation with project.
project model:
class CrmProject < ActiveRecord::Base
has_one :crm_team
team model
class CrmTeam < ActiveRecord::Base
belongs_to :crm_project
accepts_nested_attributes_for :crm_project
belongs_to :crm_section
belongs_to :manager, class_name: "User"
has_many :users
accepts_nested_attributes_for :users
end
When submitting the form to create a new team i get this error:
ActiveModel::MissingAttributeError in CrmTeamsController#create
can't write unknown attribute `crm_team_id`
and log from server :
Parameters: {"crm_team"=>{"crm_project"=>"5", "manager"=>"3", "user_ids"=>["", "2"]}, "co
mmit"=>"Create Crm team"}
User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1
[["id", 1]]
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 2]]
(0.1ms) begin transaction
User Exists (0.2ms) SELECT 1 AS one FROM "users" WHERE ("users"."email" = 'email#gmail.com' AND "users"."
id" != 2) LIMIT 1
SQL (0.2ms) INSERT INTO "crm_teams" ("created_at", "updated_at") VALUES (?, ?) [["created_at", "2020-03-1
1 07:29:19.735115"], ["updated_at", "2020-03-11 07:29:19.735115"]]
(0.2ms) rollback transaction
Completed 500 Internal Server Error in 9ms (ActiveRecord: 1.0ms)

Answer 1

When you use a has_one relation like this
has_one :crm_team
Rails expects you to add crm_team_id to your crm_project, in order to understand which crm_team is related with crm_project object. Adding it going to solve your problem.
In my opinion defining opposite like this much better in logic. Because in future these teams can have multiple projects.
class CrmProject < ActiveRecord::Base
belongs_to :crm_team
class CrmTeam < ActiveRecord::Base
***has_one/has_many(pick one)*** :crm_project
accepts_nested_attributes_for :crm_project
belongs_to :crm_section
belongs_to :manager, class_name: "User"
has_many :users
accepts_nested_attributes_for :users
end