私のプロジェクトにはいくつかのモデルがあります。それらのいくつかがあります:QualificationとCurriculum. Qualification子供がいます（カリキュラム）。Qualification削除するときに、すべての子を削除することを確認したいと思います。これが私のコードです：
# Table name: qualifications
#
# id :integer not null, primary key
# subject_id :integer
# teacher_id :integer
# created_at :datetime not null
# updated_at :datetime not null
class Qualification < ActiveRecord::Base
belongs_to :subject
belongs_to :teacher
has_many :curriculums, :dependent => :delete_all
has_many :school_classes, :through => :curriculums
end
# id :integer not null, primary key
# school_class_id :integer
# qualification_id :integer
# created_at :datetime not null
# updated_at :datetime not null
class Curriculum < ActiveRecord::Base
belongs_to :school_class
belongs_to :qualification
has_one :result
has_many :timetables
end
ご覧のとおり:dependent => :delete_all、資格モデルで使用しようとしました。しかし、うまくいきません。なんで？
更新:
編集時にビューのチェックボックスをオフにして資格を削除します。
<div class="control-group">
<%= f.label :subject_ids, "Teacher can teach such subjects in the school",
:class => "control-label" %>
<div class="controls">
<table class="table table-bordered table-striped">
<thead>
<tr>
<th>Choose</th>
<th>Subject</th>
</tr>
</thead>
<tbody>
<%= hidden_field_tag "teacher[subject_ids][]", nil %> <%# We use hidden field because it doesn't submit unchecked fields. So, we pass nil and nothing will be submitted.%>
<% @subjects.each do |subject| %>
<tr>
<td>
<%= check_box_tag "teacher[subject_ids][]", # [] brackets tells that this is array.
subject.id, # Value of checkbox.
@teacher.subject_ids.include?(subject.id), # Here we automatically check checkboxes.
id: dom_id( subject ) %> <%# Give unique id for each value. 'dom_id' is Rails helper. We will have ids like: 'subject_1', 'subject_2' and etc. %>
</td>
<td>
<%= label_tag dom_id( subject ), subject.subject_name %> <%# Put name of subject. %>
</td>
</tr>
<% end %>
</tbody>
</table>
</div>
</div>
詳細は次のとおりです。
class Teacher < ActiveRecord::Base
has_many :qualifications
has_many :subjects, :through => :qualifications
end
class Subject < ActiveRecord::Base
has_many :qualifications
has_many :teachers, :through => :qualifications
end
モデルを更新するときの SQL コードは次のとおりです。
Started PUT "/teachers/2" for 127.0.0.1 at 2012-06-03 18:34:44 +0400
Processing by TeachersController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"ZJNNV9/TO6k18O1Ar1kpkU+PWbd7btHm9Tc067iMNO4=", "teacher"=>{"teacher_last_name"=>"Last", "teacher_first_name"=>"First", "teacher_middle_name"=>"Middle", "teacher_sex"=>"m", "teacher_birthday"=>"1980-12-01", "teacher_phone_attributes"=>{"teacher_mobile_number"=>"88283686", "teacher_home_number"=>"5112787", "id"=>"2"}, "teacher_education_attributes"=>{"teacher_education_university"=>"Mmm", "teacher_education_year"=>"1970-01-01", "teacher_education_graduation"=>"Graduated", "teacher_education_speciality"=>"Math", "id"=>"2"}, "teacher_category"=>"1st", "subject_ids"=>["", "4", "3", "1"]}, "commit"=>"Update", "id"=>"2"}
User Load (0.5ms) SELECT "users".* FROM "users" WHERE "users"."id" = 2 LIMIT 1
Teacher Load (0.4ms) SELECT "teachers".* FROM "teachers" WHERE "teachers"."id" = $1 LIMIT 1 [["id", "2"]]
(0.1ms) BEGIN
Subject Load (0.5ms) SELECT "subjects".* FROM "subjects" WHERE "subjects"."id" IN (4, 3, 1)
Subject Load (0.5ms) SELECT "subjects".* FROM "subjects" INNER JOIN "qualifications" ON "subjects"."id" = "qualifications"."subject_id" WHERE "qualifications"."teacher_id" = 2
SQL (0.4ms) DELETE FROM "qualifications" WHERE "qualifications"."teacher_id" = 2 AND "qualifications"."subject_id" = 2
TeacherPhone Load (0.4ms) SELECT "teacher_phones".* FROM "teacher_phones" WHERE "teacher_phones"."teacher_id" = 2 LIMIT 1
TeacherEducation Load (0.4ms) SELECT "teacher_educations".* FROM "teacher_educations" WHERE "teacher_educations"."teacher_id" = 2 LIMIT 1
(24.1ms) COMMIT
Redirected to http://0.0.0.0:3000/teachers
Completed 302 Found in 57ms (ActiveRecord: 27.2ms)