Django admin ManyToMany inline “has no ForeignKey

Question

I'm setting up the Django admin to the following models:

class Quote(models.Model):                                                  
    author = models.CharField(max_length=100)                               
    quote = models.CharField(max_length=1000)                               
    tags = models.ManyToManyField('Tag')                                    

class Tag(models.Model):                                                    
    name = models.CharField(max_length=100)                                 

With the following code:

class TagInline(admin.TabularInline):                                                                                               
    model = Tag                                                             

class QuoteAdmin(admin.ModelAdmin):                                         
    list_display = ('author', 'quote')                                      
    inlines = (TagInline,)                                                  

class TagAdmin(admin.ModelAdmin):                                           
    pass                                                                    

admin.site.register(Quote, QuoteAdmin)                                      
admin.site.register(Tag, TagAdmin)

When trying to view the admin page to add a Quote, the page shows an error saying <class 'quotes.models.Tag'> has no ForeignKey to <class 'quotes.models.Quote'>. This didn't happen before I added an inline. What's the problem? How do I correctly add a Tag as an inline?

(I spent a good 20 minutes searching for an answer; I found similar questions but none of their answers worked for me.)

Answer 1

Admin documentation has a section dedicated to inlining with many-to-many relationships. You should use Quote.tags.through as a model for TagInline, instead of Tag itself.