# 4.刪除
# 在修改記錄頁面左下角添加一個刪除按鈕,一個鏈接,跳轉至一個提示刪除內容的頁面,確認刪除；
#     關聯刪除,刪除記錄同時也刪除外鍵的關聯表;
    # table_obj_common.html
       <div class="form-group">
            <div class="col-sm-10">
                <a href="{% table_obj_delete app_name model_name form_obj.instance.id %}">DELETE</a>
            </div>
        </div>
    #
 
 urls.py
        url(r‘^(\w+)/(\w+)/(\d+)/add/$‘, views.table_obj_delete, name="table_obj_delete"),
    # views.py
        @login_required
        def table_obj_delete(app_name,model_name,obj_id):
            """刪除記錄"""
            admin_class = site.enabled_admins[app_name][model_name]
            obj 
 
= admin_class.model.objects.get(id=obj_id)
            return render(request, ‘kingadmin/table_obj_delete.html‘,locals())
    # table_obj_delete.html
        delete {{ obj }}
        <!-- obj代表當前這條記錄 -->

# 在刪除頁面確認,後臺刪除該記錄;
#     >> a = models.CustomerInfo.objects.first()
#     >> a.delete()  # 會不會刪除關聯的表數據?會;|跟蹤記錄表;
 

# django-admin在刪除時顯示友好提示,列出所有關聯表;

# 一層層遞歸所有外鍵,刪除;
    # table_obj_delete.html
        {% display_all_related_objs obj as all_related_obj_eles%}
        {{ all_related_obj_eles|safe }}
    # kingadmin_tag.py
        @register.simple_tag
        def display_all_related_objs(obj):
            """顯示要被刪除對象的所有關聯對象"""
            ele = "<ul>"
            ele += "<li>%s</i>"%obj
            # 1.forignkey | get_internal_type()
            for reversed_fk_obj in obj._meta.related_objects:
                related_table_name = reversed_fk_obj.name
                related_lookup_key = "%s_set"%related_table_name
                # >> getattr(a,‘customerinfo_set‘) # 獲取關聯表
                # >> getattr(a,‘customerinfo_set‘).all() # 關聯表所有對象
                related_objs = getattr(obj,related_lookup_key).all() # 反向查所有關聯數據
                ele += "<li>%s</li><ul>"%related_table_name
                # 如果是many_to_many就不需要深入遞歸,打印影響的數據
                if reversed_fk_obj.get_internal_type() == "ManyToManyField":
                    for i in related_objs:
                        ele += "<li><a href=‘/kingadmin/%s/%s/%s/change/‘>%s</a> 記錄中與%s相關數據將被刪除</li>" % (i._meta.app_label,i._meta.model_name,i.id,i, obj) # 課程相關
                else:        
                    for i in related_objs:
                        ele += "<li>%s</li>" % i
                        ele += display_all_related_objs(i) # 調用自己,遞歸查找
                    
                ele += "<ul></li>"
            ele += "</ul>"
            return ele
                    
    # >> a._meta.fields  # 獲取所有字段
    # >> a._meta.fields_map # 外鏈的表映射
    # (‘student‘:<ManyToOneRel:crm.student>,...)
    # >> from crm import models
    # >> a = models.CustomerInfo.objects.all()[1]
    # >> a
    # <CustomerInfo: ‘大西瓜‘> # 學員表中的學生是外鍵關聯著客戶表的;一對多反向查詢(外鍵設置在student);
    # >> a.student_set.select_related() # 獲取當前查詢對象的所有外鍵字段對應表的查詢集：student
    # <QuerySet [<Student:‘大西瓜‘ >]>
    
    # 只要a._meta.fields_map遇到ManyToOneRel的,就反向去查找：
    
    # 要考慮自關聯,referer_from 轉介紹
    # >> a._meta.fields_map
    # (...‘customerinfo‘:<ManyToOneRel:crm.student>...) # 映射中含有當前的表,忽略;
    
    # 綜合：
    # //////a._meta.fields可以獲得所有foreignkey # 不需要管,學生刪除不影響客戶表;
    # a._meta.related_obj 可以獲取所有反向關聯;而不使用a._meta.fields_map,因為有個臟數據需要判斷;
    # a._meta.many_to_many可以獲取多對多關系的數據;
        
    # 多層級遞歸刪除
        # 課程-班級-上課記錄-學習記錄；
        # 課程被刪除,與之多對多關系的客戶信息不會被刪除,但是字段會收到影響;
        
    # 給展示記錄添加鏈接跳轉查看
    ele += "<li><a href=‘/kingadmin/%s/%s/%s/change/‘>%s</a> 記錄中與%s相關數據將被刪除</li>" % (app_name,model_name,i.id,i, obj)
    {% display_all_related_objs i._meta.app_label,i._meta.model_name,i.id,i, obj as all_related_obj_eles%}
    
    # table_obj_delete.html | 點擊刪除所有關聯數據
        <form method=‘post‘>
            {% csrf_token %}
            <input type=‘submit‘ class=‘btn btn-danger‘ value=‘確認刪除‘>
            <a>返回</a>
        </form>
    # views.py
        @login_required
        def table_obj_delete(app_name,model_name,obj_id):
            """刪除記錄"""
            admin_class = site.enabled_admins[app_name][model_name]
            obj = admin_class.model.objects.get(id=obj_id)
            if request.method == ‘POST‘:
                obj.delete()
                return redirect(‘/kingadmin/{app_name}/{model_name}/‘.format(app_name=app_name,model_name=model_name))
            return render(request, ‘kingadmin/table_obj_delete.html‘,locals())

CRM手記- 12 | Django