在Django的ManyToManyField中显示多个实例

Question

Here's what I have in the image:

I would like to display what I colored in green. Basically I would like to display what each product cost. For Bob he cost $12010 and Jill cost $12010 for a total price of $24020.

Here's my code so far:

class PurchaseOrder(models.Model):
    product = models.ManyToManyField('Product', null =True)

    def get_products(self):
        return "<BR> </BR>".join([p.products for p in self.product.all()])
    get_products.allow_tags = True

class Product(models.Model):
    products = models.CharField(max_length=256, null =True)
    price_for_each_item = models.FloatField() #Here is what I want to be displayed as green

How can I do this? Notice that each product gets a new line. So I'm trying to get each indivdual item on the same line as that indivdual item's price. For example here is,

Bob $12010.0

Jill $12010.0

Answer 1

You can use string concatenation to concatenate the name with the price. If products should be the first part of the string and price_for_each_item the second part, use:

def get_products(self):
    return "<br />".join("%s %s" % (p.products, p.price_for_each_item) for p in self.product.all())

A few unrelated comments:
Note that, according to the XHTML standards (and recommended by the HTML standard), a tag without any real content, like the <br> tag should be self-closing (thus <br /> instead of <br> </br> ).

Also, removing the square brackets inside the join function will create a generator instead of a list. This will not create a (useless) intermediary list in memory and the process will be slightly faster. I think it's a good habit to develop in case you ever have to work with large lists where the reduced memory needs are substantial.

And another note, null=True doesn't do anything on a ManyToManyField . null=True removes the NOT NULL clause on the database-level, but m2m relations are saved in a separate table entirely. If a model has no related models in a m2m relation, there are simply no records in the m2m table.