#利用cbv的繼承特性，進行views中程式碼優化

#把views中的程式碼拆出來，新建custom_view.py，把cbv-class從views中挪進去

#自定義view，custom_view.py中新建一個BaseView 用於定義條件變數
import datetime
from itertools import chain

from django.core.paginator import Paginator
from django.db.models import Model
from django.http import JsonResponse
from django.views import
 
 View
from example import models

def model_to_dict(instance, fields=None, exclude=None):
    opts = instance._meta
    data = {}
    for f in chain(opts.concrete_fields, opts.private_fields, opts.many_to_many):
        if fields and f.name not in fields:
            continue
        if exclude and f.name in
 
 exclude:
            continue
        value = f.value_from_object(instance)
        if isinstance(value, datetime.datetime):
            value = value.strftime('%Y-%m-%d %H:%M:%S')
        if isinstance(value, datetime.date):
            value = value.strftime('%Y-%m-%d')
        data[f.name] = value
    
 
return data

#BaseView中定義條件變數
class BaseView(View):
    model_class = None   #1-傳遞類變數
    fields = []          #2-返回指定欄位
    exclude_fields = []  #3-指定返回時過濾掉哪些欄位
    filter_fields = []  #4-按照什麼欄位進行過濾
    search_fields = []  #5-按照什麼欄位進行模糊匹配，前端傳key=search的欄位

    #1-驗證model_clsss不傳的時候
    @property
    def model(self):
        #issubclass:引數1是不是引數2的子類，校驗model_class
        if self.model_class and issubclass(self.model_class,Model):
            return self.model_class
        raise Exception("未定義model_class")

    def get_filter_dict(self):
        filter_dict = {}
        for filed in self.filter_fields:
            #通過request取到name值
            value = self.request.GET.get(filed)
            if value:
                filter_dict[filed] = value
        return filter_dict

    def get_search_dict(self):   #只能模糊查詢一個欄位
        search_dict = {}
        value = self.request.GET.get('search')
        if value:
            search_dict = {"%s__contains" %self.search_fields[0]:value}
        return search_dict

def get_search_dict2(self): #實現多個欄位模糊匹配,欄位間是or的關係
    q = Q()   #空Q，什麼條件都沒有
    value = self.request.GET.get('search')
    if value:
        for filed in self.search_fields:
            d ={"%s__contains" %filed:value}
            q  = Q(**d) |q
    return q#把複用介面方法變成共用方法，
class GetView(BaseView):
    def get(self,requests):
        # get請求時  獲取傳遞過來的第幾頁資料
        page = requests.GET.get('page')
        filter_dict = self.get_filter_dict()
        search_dict = self.get_search_dict()
        search_q = self.get_search_dict2()

        #增加過濾條件，獲取查詢結果
        qs = self.model_class.bojects.filter(is_delete=0).filter(filter_dict).filter(**search_dict).filter(search_q)
        page_obj = Paginator(qs, 5)
        # 獲取第幾頁的資料
        page_data = page_obj.get_page(page)
        # 用於儲存返回的dict型別資料
        data_list = []
        for data in page_data:
            # 通過 model_to_dict轉換成dict，exclude過濾哪些欄位
            tmp_data = model_to_dict(data, fields=self.fields,exclude=self.exclude_fields)
            data_list.append(tmp_data)
        return JsonResponse({"code": 0, "data": data_list})

#老的views中只需傳入條件：

from .custom_view import GetView

#簡化程式碼 ,繼承
class SParameter(GetView):
    model_class = models.Parameter   #1-重寫類變數，指定操作的資料
    fields = ['name']                #2-指定返回name欄位
    exclude_fields = ['name']        #3-返回欄位過濾掉name欄位
    filter_fields = ['name']         #4-按照name進行過濾
    search_fields = ['name']         #5-按照name進行模糊匹配

#同時urls優化，在子專案下建立一個urls.py

#子urls引用custom_views邏輯
from django.urls import path
from .views import f_parameter,SParameter

urlpatterns = [
    # fbv
    path('f_parameter', f_parameter),
    # cbv
    # path('c_parameter', Parameter.as_view()),
    # 優化程式碼後cbv路由
    path('s_parameter', SParameter.as_view()),
]

#老urls中再引用子專案下的urls

from django.urls import path,include
from example import urls

urlpatterns = [

    #通過include 將其他app的路由匯入進來
    #api是base目錄，每個example當中的路由都會加上api/
    path('api/',include(urls)),
]