使用has_many创建记录：通过？

Question

我有以下型号：

class Department < ApplicationRecord 
    has_many :department_job_titles 
    has_many :job_titles, through: :department_job_titles 
end 

class JobTitle < ApplicationRecord 
    has_and_belongs_to_many :departments 
end 

class DepartmentJobTitle < ApplicationRecord 
    belongs_to :department 
    belongs_to :job_title 
    validates :department_id, uniqueness: { scope: :job_title_id } 
end 

这是犯错误的W¯¯PG::UndefinedColumn: ERROR: column department_job_titles.title does not exist LINE 1: ... "department_job_titles"."department_id" = $1 AND "departmen...

Department.first.department_job_titles.find_or_create_by(title: title) 

DepartmentJobTitle具有以下字段：id, department_id, job_title_id

什么我错在这里做什么？由于

Answer 1

试试这个：

job_title = JobTitle.find_or_create_by(title: title) 
Department.first.job_titles << job_title unless job_title.in? Department.first.job_titles 

或者说，第二行可能是：

另外：

class JobTitle < ApplicationRecord 
    has_many :department_job_titles 
    has_many :departments, through: :department_job_titles 
end 

......还有......

class DepartmentJobTitle < ApplicationRecord 
    belongs_to :department 
    belongs_to :job_title 
    validates :department, presence: true, uniqueness: { scope: :job_title } 
    validates :job_title, presence: true 
end 

...并考虑你想要什么样的行为，如果有人摧毁了JobTitle或Department - 要么也要销毁DepartmentJobTitle，要么防止destroy被阻止。