Re: Please I need help on how to create a custom method for a model with list_display

Thanks very much. I have solved the problem. 

On Sunday, May 20, 2018, Daniel Germano Travieso <danielgtravieso@gmail.com> wrote:

Hello!

On your case, as stated on the official doc, you should just create a method on the model you want to display the ManyToMany field on the list_display that maybe returns the list of items from the ManyToMany field. Django avoids using this as it could be a potential overhead as you will run seperate queries on the database to fetch all the related many-to-many objects.

But if you are feeling adventurous, just create the method that performs that query.

i.e. On your Book model you create a method that returns the self.authors.all() set. Then you use that method's name on the list_display instead of authors.

Hope it helps.

On Saturday, May 19, 2018 at 3:54:17 PM UTC-3, Godson Rapture wrote:

Please I am learning Django 2.0.4

Right now I am learning about Django Admin.

I got an error that the value of my list_display should not be a ManyToMany Field.

I referred back to Django official doc and I was asked to create a custom method for my model.

I tried looking for an example of how to do that, I could not see.

Here is my model.py program

 from django.db import models    class Publisher(models.Model):      name = models.CharField(max_length=30)      address = models.CharField(max_length=50,blank=True)      city = models.CharField(max_length=60,blank=True)      country = models.CharField(max_length=50,blank=True)      website = models.URLField()      def __str__(self):          return self.name    class Author(models.Model):      salution = models.CharField(max_length=10)      first_name = models.CharField(max_length=30)      last_name = models.CharField(max_length=40)      email = models.EmailField()      headshot = models.ImageField(upload_to = "tmp")      def __str__(self):          return f"{self.first_name} {self.last_name}"    class Book(models.Model):      title = models.CharField(max_length=100)      authors = models.ManyToManyField(Author)      publisher = models.ForeignKey(Publisher,on_delete=models.CASCADE,)      publication_date = models.DateField()      def __str__(self):          return self.title  

Here is my admin.py program

from django.contrib import admin  from polls.models import Book, Publisher, Author  # Register your models here.    class BookAdmin(admin.ModelAdmin):      list_display = [          "title",          "authors", #a ManyToMany Field        ]       search_fields = [          "Book"      ]      class Meta:          model = Book    admin.site.register(Book, BookAdmin)  

Can someone please help me.

Thanks.

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