python - ModelForm 用空字段保存模型数据

Question

我正在使用 Django 中的 ModelForm 为我的数据库中的模型构建一个编辑表单。表单中的每个字段都是可选的，因为用户可能只想编辑一个字段。

我遇到的问题是，当我在 View 中调用 save() 时，所有空字段都被保存在实例的原始值上(例如，如果我只输入一个新的 first_name ，last_name和ecf_code字段会在对应的实例中保存一个空字符串。)

形式:

class EditPlayerForm(forms.ModelForm):

    class Meta:
        model = Player
        fields = ['first_name', 'last_name', 'ecf_code']

    def __init__(self, *args, **kwargs):
        super(EditPlayerForm, self).__init__(*args, **kwargs)
        self.fields['first_name'].required = False
        self.fields['last_name'].required = False
        self.fields['ecf_code'].required = False

View :

def view(request, player_pk = ''):

    edit_player_form = forms.EditPlayerForm(auto_id="edit_%s")

    if "edit_player_form" in request.POST:

        if not player_pk:

            messages.error(request, "No player pk given.")

        else:

            try:

                selected_player = Player.objects.get(pk = player_pk)

            except Player.DoesNotExist:

                messages.error(request, "The selected player could not be found in the database.")
                return redirect("players:management")

            else:

                edit_player_form = forms.EditPlayerForm(
                    request.POST,
                    instance = selected_player
                )

                if edit_player_form.is_valid():

                    player = edit_player_form.save()
                    messages.success(request, "The changes were made successfully.")
                    return redirect("players:management")

                else:
                    form_errors.convert_form_errors_to_messages(edit_player_form, request)

    return render(
        request,
        "players/playerManagement.html",
        {
            "edit_player_form": edit_player_form,
            "players": Player.objects.all(),
        }
    )

我已经尝试重写表单的 save() 方法来显式检查哪些字段在 POST 请求中有值，但这似乎没有任何效果也有区别。

尝试覆盖保存方法:

def save(self, commit = True):

    # Tried this way to get instance as well
    # instance = super(EditPlayerForm, self).save(commit = False)

    self.cleaned_data = dict([ (k,v) for k,v in self.cleaned_data.items() if v != "" ])

    try:
        self.instance.first_name = self.cleaned_data["first_name"]
    except KeyError:
        pass

    try:
        self.instance.last_name = self.cleaned_data["last_name"]
    except KeyError:
        pass

    try:
        self.instance.ecf_code = self.cleaned_data["ecf_code"]
    except KeyError:
        pass


    if commit:
        self.instance.save()


    return self.instance

我也没有为 Player 模型设置任何默认值，因为文档说 ModeForm 将使用这些值作为表单提交中不存在的值。

编辑:

这是整个 EditPlayerForm:

class EditPlayerForm(forms.ModelForm):


    class Meta:
        model = Player
        fields = ['first_name', 'last_name', 'ecf_code']

    def __init__(self, *args, **kwargs):
        super(EditPlayerForm, self).__init__(*args, **kwargs)
        self.fields['first_name'].required = False
        self.fields['last_name'].required = False
        self.fields['ecf_code'].required = False


    def save(self, commit = True):

        # If I print instance variables here they've already
        # been updated with the form values

        self.cleaned_data = [ k for k,v in self.cleaned_data.items() if v ]

        self.instance.save(update_fields = self.cleaned_data)

        if commit:

            self.instance.save()

        return self.instance

编辑:

好的，这就是解决方案，我想我会把它放在这里，因为它可能对其他人有用(我当然从中学到了一些东西)。

事实证明，模型表单的 is_valid() 方法实际上对您传递到表单中的实例进行了更改，为 save() 做好了准备方法来保存它们。所以为了解决这个问题，我扩展了表单的clean()方法:

 def clean(self):

    if not self.cleaned_data.get("first_name"):
        self.cleaned_data["first_name"] = self.instance.first_name

    if not self.cleaned_data.get("last_name"):
        self.cleaned_data["last_name"] = self.instance.last_name

    if not self.cleaned_data.get("ecf_code"):
        self.cleaned_data["ecf_code"] = self.instance.ecf_code

这基本上只是检查字段是否为空，如果字段为空，则用给定实例中的现有值填充它。 clean() 在用新的表单值设置实例变量之前被调用，所以这样，任何空字段实际上都被相应的现有实例数据填充。

Answer 1

您可以使用 update() 方法代替 save()或参数 update_field

self.instance.save(update_fields=['fields_to_update'])

通过仅使用非空值构建列表 ['fields_to_update']。

它甚至应该适用于您已经尝试过的理解:

self.cleaned_data = [ k for k,v in self.cleaned_data.items() if v ]

self.instance.save(update_fields=self.cleaned_data)

编辑:

不覆盖保存方法(并在表单中注释掉此尝试):

not_empty_data = [ k for k,v in edit_player_form.cleaned_data.items() if v ]
print(not_empty_data)
player = edit_player_form.save(update_fields=not_empty_data)