Django 管理页面：通过多个模型选择而不是原始文本自定义 ID 的字典 (JSONField)

Question

Django 管理页面：通过多个模型选择而不是原始文本自定义 ID 的字典 (JSONField)

Bor*_*jaX 4 python django customization django-admin django-jsonfield

我有一个模型，其中一个字段是postgres.fields.JSONField。

将要存储在那里的 Json 是引用数据库中其他项目（可能的关系/属性）的 ID 变量字典。

请允许我更具体：

基本上，我正在尝试创建一个折扣系统，其中某些折扣适用于某些产品。JSON 字段包含了解哪些产品可以获得折扣的约束。

例如：

如果我想对属于“饮料”类别的所有产品应用 50% 的折扣，并且“饮料”类别5在数据库中具有 id ，则折扣记录将如下所示：
```
discount_type='percent'
discount='0.5'
filter_by={
    'category': [5]
}
```
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如果我想$ 20 off适用于所有产品的“饮料”类别和由制造，比方说，可口可乐，该filter_by词典将如下所示：

discount_type='fixed amount'
discount='20'
filter_by={
    'category': [5],
    'manufacturer': [2]   # Assuming coca-cola is the Manufacturer 
                          # with id==2 in the 'Manufacturers'
                          # table of the database (NOTE: this is 
                          # needed since CocaCola manufactures
                          # products besides "Beverages")
}

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如果我想对特定产品（比方说产品id是3）应用 25% 的折扣，字典将如下所示：
```
discount_type='percent'
discount='0.25'
filter_by={
    'id': [3]
}
```
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这个想法似乎对我的需要足够灵活，我很高兴（到目前为止）。

现在，问题是如何在模型的 Django 管理区域中输入这些值Discount。

正如预期的那样，filter_by字典呈现为文本字段，最初如下所示：

If I want to add fields to it, I need to write the exact JSON of what I want... Which means that if I want to apply a discount to the "Beverages" category, I need to go figure out which ID that category has in the database, and then manually type {"category": [5]}, while being extremely careful when typing the ', the :, make sure that I don't miss a ] or a [...

Thaaaat... well, that is not very helpful...

Since I am only going to be filtering by a few fields (category, manufacturer, product...) which are actually lists of IDs of other elements of the database, I would like to show a big MultiSelect box per thingy I can filter for, so I can see a user friendly list of all the elements I can filter by, select a few, and then, when I click on "Create discount", I would get the filter_by dictionary (I'm still far from worrying about how to generate the dictionary, since I don't even know how to properly render the Admin form).

Something like what Django Admin automatically did for my Products' categories:

That is really, really, nice: One product can belong to several categories. For that, Django renders, side by side, two <select multiple boxes, with the available categories, and the categories that the product already belongs to... I can add/remove categories through the stroke of a mouse... Really, really nice. But Django can do that because it knows that the categories are a ManyToMany relation in the Product model.

class Product(models.Model):
    parent = models.ForeignKey('self', null=True, blank=True)
    manufacturer = models.ForeignKey('Manufacturer')
    categories = models.ManyToManyField('Category',
                                         related_name='products', blank=True)

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The problem with the Discount model is that there is no ManyToMany field to category, manufacturer or product. Poor Django doesn't know that a Discount is related to all those things: It only knows there's a Json field.

I would really like to be able to show a bunch of those <select> in the Django Area listing all the possible filters (Category, Manufacturer, ID...) that can be stored in the filter_by dictionary (one entry with the double <select> for Category showing all the available categories in the database, one entry for Manufacturer, showing all the available manufacturers... etcetera). But I really, really don't know how to do that.

I could bore you with a bunch of tries I've done, using Widgets, trying to represent the JSON field through a form, through forms.ModelMultipleChoiceField (which by the way, seems to have been the closest thing to what I want, although still very far)... But I think that is kind of pointless, since nothing came close to what I wanted.

As usual, thank you for reading this huge email and thank you in advance. Any hint will be really appreciated, even just a you should take a look to "this"

Answer 1

Bor*_*jaX 6

所以......我很欣赏@alfonso.kim 的回答，但是为了“渲染”目的而创建一个全新的 Django 模型的想法对我来说听起来有点矫枉过正。请！不要误会我的意思：这可能是做这件事（我见过的方法推荐很多次）的“规范”的方式，也许是比什么更好的我没有，但我想表现怎么我解决我的问题，特别是：

我查看了 Django 的源代码，特别是如何ManyToMany在 Admin 中显示关系。如果您查看我上面的原始问题，我想弄清楚 Django在编辑一个产品时使用哪个类来显示类别（即“双列选择”，给它一个我非常喜欢的名称）。事实证明它是一个django.forms.models.ModelMultipleChoiceField，“经验丰富”，带有FilteredSelectMultiple小部件的提示。

有了这些信息，我为我的班级创建了一个自定义管理表单Coupon，手动添加了我想要显示的字段：

class CouponAdminForm(forms.ModelForm): brands = forms.ModelMultipleChoiceField( queryset=Brand.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Brands", is_stacked=False)) categories = forms.ModelMultipleChoiceField( queryset=Category.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Categories", is_stacked=False)) products = forms.ModelMultipleChoiceField( queryset=Product.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Products", is_stacked=False)) def __init__(self, *args, **kwargs): # ... we'll get back to this __init__ in a second ... class Meta: model = Coupon exclude = ('filter_by',) # Exclude because we're gonna build this field manually
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然后告诉ModelAdmin我的优惠券班级使用该表格而不是默认表格：

class CouponsAdmin(admin.ModelAdmin): form = CouponAdminForm # ... # admin.site.register(Coupon, CouponsAdmin)
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这样做会在公式的根部显示三个表单的手动添加字段（brand、categories和products）。换句话说：这在与我的模型中的其他字段相同的级别上产生了三个新字段。但是：它们并不是真正的“一流”字段，因为它们实际上是要确定我的模型（字段）中一个特定字段的内容，让我们记住，它是一个或多或少看起来像的字典：CouponCoupon.filter_by

filter_by = { "brands": [2, 3], "categories": [7] }
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为了让使用 Admin 网页的人清楚这三个字段在 Coupon 模型中并不是“真正的”第一级字段，我决定将它们分组显示。

为此，我需要更改CouponsAdmin字段的布局。我不希望这个分组影响我Coupon模型的其他字段的显示方式，即使新字段后来添加到模型中，所以我让表单的所有其他字段保持不变（换句话说：只应用特殊/分组布局到brands,categories和products表单中的字段）。令我惊讶的是，我无法在ModelForm课堂上做到这一点。我不得不去ModelAdmin（我真的不知道为什么......）：

class CouponsAdmin(admin.ModelAdmin): def get_fieldsets(self, request, obj=None): fs = super(CouponsAdmin, self).get_fieldsets(request, obj) # fs now contains only [(None, {'fields': fields})] meaning, ungrouped fields filter_by_special_fields = (brands', 'categories', 'products') retval = [ # Let every other field in the model at the root level (None, {'fields': [f for f in fs[0][1]['fields'] if f not in filter_by_special_fields] }), # Now, let's create the "custom" grouping: ('Filter By', { 'fields': ('brands', 'categories', 'products') }) ] return retval form = CouponAdminForm
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关于这里的更多信息fieldsets

这就是诀窍：

现在，当管理员用户Coupon通过此表单创建一个新表单时（换句话说：当用户单击页面上的“保存”按钮时），我将获得一个查询集，用于我在自定义表单中声明的额外字段（一个查询集用于brands，另一个用于categories和另一个用于products) 但我实际上需要将该信息转换为字典。我能够通过覆盖saveModel's Form的方法来实现这一点：

class CouponAdminForm(forms.ModelForm): brands = forms.ModelMultipleChoiceField(queryset=Brand.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Brands", is_stacked=False)) categories = forms.ModelMultipleChoiceField(queryset=Category.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Categories", is_stacked=False)) products = forms.ModelMultipleChoiceField(queryset=Product.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Products", is_stacked=False)) def __init__(self, *args, **kwargs): # ... Yeah, yeah!! Not yet, not yet... def save(self, commit=True): filter_by_qsets = {} for key in ['brands', 'categories', 'products']: val = self.cleaned_data.pop(key, None) # The key is always gonna be in 'cleaned_data', # even if as an empty query set, so providing a default is # kind of... useless but meh... just in case if val: filter_by_qsets[key] = val # This 'val' is still a queryset # Manually populate the coupon's instance filter_by dictionary here self.instance.filter_by = {key: list(val.values_list('id', flat=True).order_by('id')) for key, val in filter_by_qsets.items()} return super(CouponAdminForm, self).save(commit=commit) class Meta: model = Coupon exclude = ('filter_by',)
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这filter_by在"Save"上正确填充了优惠券的字典。

还剩下一些细节（使管理表单更加用户友好）：在编辑现有时 Coupon，我希望表单的brands,categories和products字段预先填充filter_by优惠券字典中的值。

这就是修改Form的__init__方法派上用场的地方（记住我们正在修改的实例可以在Form的属性中访问）self.instance

class CouponAdminForm(forms.ModelForm): brands = forms.ModelMultipleChoiceField(queryset=Brand.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Brands", is_stacked=False)) categories = forms.ModelMultipleChoiceField(queryset=Category.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Categories", is_stacked=False)) products = forms.ModelMultipleChoiceField(queryset=Product.objects.all().order_by('name'), required=False, widget=FilteredSelectMultiple("Products", is_stacked=False)) def __init__(self, *args, **kwargs): # For some reason, using the `get_changeform_initial_data` method in the # CouponAdminForm(forms.ModelForm) didn't work, and we have to do it # like this instead? Maybe becase the fields `brands`, `categories`... # are not part of the Coupon model? Meh... whatever... It happened to me the # same it happened to this OP in stackoverflow: /sf/ask/1874985661/ super(CouponAdminForm, self).__init__(*args, **kwargs) self.fields["brands"].initial = self.instance.filter_by.get('brands') self.fields["categories"].initial = self.instance.filter_by.get('categories') self.fields["products"].initial = self.instance.filter_by.get('products') def save(self, commit=True): filter_by_qsets = {} for key in ['brands', 'categories', 'products']: # ... explained above ...
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就是这样。

到目前为止（现在，2017 年 3 月 19 日）这似乎很好地满足了我的需要。

正如alfonso.kim在他的回答中指出的那样，除非我更改窗口的 Javascrip（或者我可能使用自定义模型？不知道：没有尝试过），否则我无法动态过滤不同的字段ChainedForeignKey我的意思是这种方法我无法过滤管理网页上的选择框，删除仅属于所选类别的产品，例如，我不能执行诸如“如果用户选择brand, 过滤器categories，products因此它们只显示属于那个牌子”。发生这种情况是因为当用户选择一个品牌时，浏览器和服务器之间没有 XHR (Ajax) 请求。基本上：流程是您获取表格-->您填写表格-->您发布表单，当用户单击表单上的“事物”时，浏览器 <--> 服务器之间没有通信。如果用户在选择中选择“可口可乐” brands，那么products选择会被过滤，并plastic bags从可用产品中删除（例如），但是很好......这种方法“足够好”满足我的需求。

请注意：此答案中的代码可能包含一些多余的操作，或者本可以写得更好的内容，但到目前为止，它似乎工作正常（谁知道，也许我必须编辑我的答案一些几天后说“我完全错了！请不要这样做！”但到目前为止似乎还可以）不用说：我欢迎任何人必须说的任何建议评论:-)

我希望这对未来的人有所帮助。

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