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POForm to swap 2 objects in database with Django
 

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  1. POForm to swap 2 objects in database with Django
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    <p>I'm new to django and I've been developing a simple application for the past month or so, but I have a problem, something I did not manage to do. I have a simple model called WeeklyPlaylist (from my models.py):</p> <pre><code>class WeeklyPlaylist(models.Model): total_num_entries_in_playlist = 8 get_pos_choices = get_integer_choices(1, total_num_entries_in_playlist) sched = models.ForeignKey(Schedule) week = models.IntegerField(choices=get_integer_choices(1, 52)) position = models.IntegerField(choices=get_pos_choices) </code></pre> <p>where 'position' simply indicates the position of a video in a playlist. I'd like to provide the admin with the ability to swap the position of one video in a playlist with another video in that same playlist, through the change/update form of the model above (from my admin.py):</p> <pre><code>class WeeklyPlaylistAdmin(admin.ModelAdmin): (...) readonly_fields = ('position',) form = WeeklyPlaylistAdminForm def get_changelist_form(self, request, obj=None, **kwargs): return WeeklyPlaylistAdminForm </code></pre> <p>and I'm defining my own form for this object (still from admin.py):</p> <pre><code>class WeeklyPlaylistAdminForm(ModelForm): class Meta: model = WeeklyPlaylist fields = ('position',) swap_with_position = forms.IntegerField(widget=forms.Select(choices=WeeklyPlaylist.get_pos_choices)) def clean_swap_with_position(self): swap_with_position = self.cleaned_data['swap_with_position'] instance = getattr(self, 'instance', None) if instance and instance.id and swap_with_position == self.instance.position: raise forms.ValidationError("You must specify a different position than the actual one.") # select the database obj to swap position with other = WeeklyPlaylist.objects.filter(sched__screen__name=self.instance.sched.screen.name, sched__year__exact=self.instance.sched.year, week=self.instance.week, position=swap_with_position) if other.count() != 1: raise forms.ValidationError("The desired position does not correspond to any existing WeeklyPlaylist entry.") return swap_with_position </code></pre> <p>What I had in my mind basically was to provide an extra 'select' html tag to the admin in the change/update form of the WeeklyPlaylist model where he could enter the new position in the playlist for the current video, with the necessary checks in the associated clean_ method to make sure the desired playlist position is valid. So far so good. Now, my problem is the following: when the admin clicks on the 'save' button, how can I simultaneously save the modified object, and the one it is exchanging its position with? I've tried doing this in the save() method of the form, using the following code:</p> <pre><code>def save(self, commit=True, *args, **kwargs): m = super(WeeklyPlaylistAdminForm, self).save(commit=False, *args, **kwargs) cleaned_data = self.cleaned_data swap_with_position = cleaned_data.get("swap_with_position") if commit: # select the database obj to swap position with other = WeeklyPlaylist.objects.get(sched__screen__name=m.sched.screen.name, sched__year__exact=m.sched.year, week=m.week, position=swap_with_position) m.position, other.position = other.position, m.position m.save() other.save() return m </code></pre> <p>That seems perfectly fine, except that for some reason, commit is always false, even though 'm' is saved after the operation is finished, which is something I don't understand. But as a consequence, other.save() is never called, and if I remove the if statement checking the value of commit, I won't be able to do a save(commit=False) on the WeeklyPlaylistAdminForm objects, which can be annoying... So, any suggestions to help me? Many thanks in advance! Cheers! Adrien</p>
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    1. USMangu Singh Rajpurohit
    1. USAdrien angeli
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    1. COCan you try removing the commit kwarg in your .save() signature and doing `commit = kwargs.get("commit", True)` instead? Just trying to rule out the Django admin internals passing a falsy 1st argument that's getting assigned to the commit kwarg. I don't think that happens, but it's something to rule out before going deeper.
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      1. POForm to swap 2 objects in database with Django
      1. USAdamKG
    2. COThanks for your comment, AdamKG, I did as you said but the result is the same and commit is still set to False...
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      1. USAdrien angeli
 

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