替代Django中的全局變量？

Question

我需要一種方法來從另一個ModelAdmin修改一個ModelAdmin成員變量。所以我雖然也許我可以使用全局變量。但是，如果有多個用戶同時使用該應用程序，那麼全局變量會不斷地發生意外變化，並且所有地獄都會崩潰。

在Django中有任何方法可以讓我從另一個ModelAdmin修改一個ModelAdmin成員變量嗎？

還是我犯了設計錯誤？我做得比實際還是難，還是我錯過了什麼？使用線程和鎖定怎麼樣？消息傳遞？活動？！？！？！幫助

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下面是整個故事。我的應用程序讓用戶通過選擇兼容的CPU，主板，內存和硬盤驅動器（按此順序）來構建PC。通過選擇一個CPU，它們僅限於帶有CPU插座的主板。通過選擇帶有DDR3 DIMM的主板，它們僅限於DDR3內存，等等。我們必須創建ManyToManyField關係，並指定中間表（帶有額外的count字段），並且指定中間表（與其他count字段一起） through arg。這要求使用InlineAdmin模型來顯示管理頁面中的字段。

令我高興的是，raw_id_field變量導致下拉小部件被一個按鈕替換，該按鈕彈出與change_list.html相同的表單，並允許用戶過濾/排序/搜索他們想要的部分。但是，這對我的老闆來說還不夠好。現在我需要根據之前的選擇對這些過濾器進行預定義（即在選擇帶有DDR3的主板後，使用DDR3過濾內存）。所以我加入了這一點：Default filter in Django admin但我需要一種方法來根據他們做出的其他選擇動態地設置CpuAdmin.default_filtersPcAdmin。

我的模型，僅包括一個簡潔零件模型：

# models.py 
class CPU(Part): 
    partNum = models.CharField(max_length=60) 
    price = models.DecimalField(precision=2) 
    socket = models.CharField(max_length=60) 
    numCores = models.CharField(max_length=60) 

class PC(models.Model): 
    name = models.CharField(max_length=60) 
    customer = models.CharField(max_length=60) 
    cpuChoices = models.ManyToManyField(CPU, through='PcCpuChoice') 
    memoryChoices = models.ManyToManyField(Memory, through='PcMemoryChoice') 
    hardDriveChoices = models.ManyToManyField(HardDrive, through='PcHardDriveChoice') 
    motherBoardChoices = models.ManyToManyField(MotherBoard, through='PcMotherboardChoice') 

class PcCpuChoice(models.Model): 
    pc = models.ForeignKey(PC, unique=False) 
    cpu = models.ForeignKey(CPU, unique=False) 
    count = models.IntegerField() 

# admin.py 
class PartAdmin(admin.ModelAdmin): 
    class Meta: 
     abstract = True 
    search_fields = ['partNum', 'description', 'model'] 
    default_filter = [] 

    def changelist_view(self, request, extra_context=None): 
     if not request.GET.has_key(self.default_filter[0]): 
      q = request.GET.copy() 
      q[self.default_filter[0]] = self.default_filter[1] 
      request.GET = q 
      request.META['QUERY_STRING'] = request.GET.urlencode() 
     return super(PartAdmin,self).changelist_view(request, extra_context=extra_context) 

class CpuAdmin(PartAdmin): 
    list_filter = ['brand', 'socket', 'numCores', 'graphics'] 
    list_display = ('partNum', 'description', 'brand', 'model', 'markupPrice', 'clockSpeed', 'watts', 'voltage') 
    default_filter = ['numCores','8'] # need to change this from PcAdmin!!! 

class PcCpuInline(admin.TabularInline): 
    model = PcCpuChoice 
    extra = 1 
    max_num = 1 
    raw_id_fields = ['cpu'] 

class PcAdmin(admin.ModelAdmin): 
    inlines = [PcCpuInline, PcMotherboardInline, PcMemoryInline, PcHardDriveInline] 

admin.site.register(PC, PcAdmin) 

Answer 1

謝謝@PeterRowell指引我在正確的方向。我用django會話來存儲過濾器，javascript向服務器發送請求，以便在它們加載表單時更新過濾器，並在它們離開表單時刪除它們，處理這些請求的一些視圖函數，添加了一個函數該模型（以請求爲參數）更新已保存的部分的過濾器，並覆蓋PartAdmin的changelist_view函數以使用request.session中的過濾器修改查詢字符串。這是很多不同文件中的很多代碼，但這裏有一些亮點可以幫助尋找這樣的解決方案的人：

發佈在問題中的所有模型都保持幾乎相同。

爲PC的觀點：

def update_filters(request): 
    try: 
     # get POST data 
     url = request.POST['form_url'] 
     id = url.split('/')[-2:-1][0] 
     system_type = url.split('/')[-3:-2][0] 

     if id is not "new": 
      system_content_type = ContentType.objects.get(app_label="systems", model=system_type.rstrip('s')) 
      system = system_content_type.get_object_for_this_type(id=id) 
      system.set_filters(request) 
     else: 
      request.session['filters'] = '' 
     return HttpResponse("Filters where updated.") 
    except: 
     return HttpResponse("Select a part and click 'Save and continue' to set the filters.") 


def delete_filters(request): 
    request.session['filters'] = '' 
    return HttpResponse("Filters where deleted.") 

下面是被放置在change_form.html的JavaScript

function post_to_url(path, params, method) { 
     method = method || "post"; // Set method to post by default, if not specified. 

     // The rest of this code assumes you are not using a library. 
     // It can be made less wordy if you use one. 
     var form = document.createElement("form"); 
     form.setAttribute("method", method); 
     form.setAttribute("action", path); 

     for(var key in params) { 
      if(params.hasOwnProperty(key)) { 
       var hiddenField = document.createElement("input"); 
       hiddenField.setAttribute("type", "hidden"); 
       hiddenField.setAttribute("name", key); 
       hiddenField.setAttribute("value", params[key]); 

       form.appendChild(hiddenField); 
      } 
     } 

     var frame = document.createElement("iframe"); 
     frame.name="hidden-form"; 
     form.target="hidden-form"; 
     document.body.appendChild(form); 
     document.body.appendChild(frame); 
     form.submit(); 
    } 

    // when they load the page, set the filters 
    $(document).ready(function(){ 
     post_to_url("/quotegenerator/systems/update_filters/",{'form_url': document.URL}); 
    }); 

    // when they exit, delete the filter cookie 
    window.onbeforeunload = function() { 
     post_to_url("/quotegenerator/systems/delete_filters/", {}); 
    } 

（通過PcAdmin add_view和change_view功能extra_context中用PARAM添加）最後，添加到PartAdmin的功能：

def set_filters(self, request): 
      # query and get the parts 
      try: 
        cpu = self.cpuChoices.get() 
      except: 
        cpu = False 
      try: 
        mobo = self.motherBoardChoices.get() 
      except: 
        mobo = False 
      try: 
        mem = self.memoryChoices.get() 
      except: 
        mem = False 
      try: 
        hdd = self.hardDriveChoices.get() 
      except: 
        hdd = False 

      # for each combo of parts, figure out whats required 
      # no parts at all 
      if not (mobo or cpu or mem or hdd): 
        request.session['filters'] = '' 
      # mobo only 
      elif mobo and not (cpu or mem or hdd): 
        request.session['filters'] = 'socket='+mobo.socket 
      # cpu only 
      elif cpu and not (mobo or mem or hdd): 
        request.session['filters'] = 'socket='+cpu.socket 
      # memory only 
      elif mem and not (mobo or cpu or hdd): 
        request.session['filters'] = 'memType='+mem.memType 
      # hard drive only 
      elif hdd and not (mobo or cpu or mem): 
        request.session['filters'] = 'interface='+hdd.interface 
      # mobo and cpu 
      elif mobo and cpu and not (mem or hdd): 
        request.session['filters'] = 'memType='+mobo.memType+'&interface='+mobo.interface 
      # mobo and memory 
      elif mobo and mem and not (cpu or hdd): 
        request.session['filters'] = 'socket='+mobo.socket+'&interface='+mobo.interface 
      # mobo and hd 
      elif mobo and hdd and not (cpu or mem): 
        request.session['filters'] = 'socket='+mobo.socket+'&memType='+mobo.memType 
      # cpu and mem 
      elif cpu and mem and not (mobo or hdd): 
        request.session['filters'] = 'socket='+cpu.socket+'&memType='+mem.memType 
      # cpu and hd 
      elif cpu and hdd and not (mobo or mem): 
        request.session['filters'] = 'socket='+cpu.socket+'&interface='+hdd.interface 
      # memory and hd 
      elif mem and hdd and not (mobo or cpu): 
        request.session['filters'] = 'memType='+mem.memType+'&interface='+hdd.interface 
      # mobo cpu and mem 
      elif cpu and mobo and mem and not hdd: 
        request.session['filters'] = 'interface='+mobo.interface 
      # mobo cpu and hd 
      elif mobo and cpu and hdd and not mem: 
        request.session['filters'] = 'memType='+mobo.memType 
      # mobo hd and mem 
      elif mobo and mem and hdd and not cpu: 
        request.session['filters'] = 'socket='+mobo.socket 
      # cpu mem and hd 
      elif cpu and mem and hdd and not mobo: 
        request.session['filters'] = 'socket='+cpu.socket+'&memType='+mem.memType+'&interface='+hdd.interface 
      # all parts 
      else: 
        request.session['filters'] = '' 

哦，和cha PartAdmin的ngelist_view功能確實有點變化：

def changelist_view(self, request, extra_context=None): 
    if ('filters' in request.session): 
     q = request.GET.copy() 
     for filter in request.session['filters'].split('&'): 
      key, value = urllib.splitvalue(filter) 
      # check if the request does not already use the filter 
      # and that the model has the attribute to filter for 
      if (not request.REQUEST.has_key(key)) and (key in self.list_filter): 
       q[key] = value 
     request.GET = q 
     request.META['QUERY_STRING'] = request.GET.urlencode() 
    return super(PartAdmin,self).changelist_view(request, extra_context=extra_context) 

Answer 2

這不是一個答案，而是在正確的方向輕推。

還有更多的變量上下文local和global。在你的情況下，上下文是user或者可能是build（如果用戶有多個同時進行的構建）。

請注意，changelist_view()方法需要一個request對象。從這裏你可以得到user，session（以及任意數量的東西）以及所有其他方式的良好狀態信息。一個進一步的觀察：在一個多線程，多進程的Web環境中，從你習慣的角度來看，確實沒有「全局」。雖然可能在這樣的環境中創建一個「全局」（例如使用memcached），但您將不得不努力工作。