Inserting Data in Datastore - App Engine - One to Many

Question

I am a beginner in GAE and python. I am having trouble understanding how to insert data with One-to-Many relationship and I don't know much about what I am doing.

I am trying to create an inventory app. Basically, I wanted to insert products under the one category each.

My db Models are below.

class Category(db.Model):
    category = db.StringProperty()
    date = db.DateTimeProperty(auto_now_add=True)

class Product(db.Model):
    ref_category = db.ReferenceProperty(Category)
    name = db.StringProperty()

I was able to insert category in the Datastore but products per category is where I am having problem with.

I have a form like below which is I am not sure if this is the correct way too. Is inserting using the key in hidden input fine as well?

<form action="/addproduct" method="post">
        <div><label>Product Name:</label><br /><input type="name" name="name" /></div>
        <div><input type="hidden" name="ref_category" value="{{selected_category.key()}}" /></div>
        <input type="submit" value="Add Candidate">
        </form>

Then, my code for insert is below which is I am having trouble. I am trying to understand the resources provided online but my brain cells cannot process it anymore.

def post(self):
        product = Product()
        product.name = self.request.get('name')
        product.ref_category = self.request.get('ref_category') 
        product.put()

I hope someone help me to understand when solution provided.

Answer 1

You're attempting to set a string to a ReferenceProperty because self.request.get return type of string. The 'ref_category' field of Product is a db.ReferenceProperty, which takes a db.Key or a Category object, but you're attempting to set it to a string.

You can do like this :

def post(self):
    product = Product()
    product.ref_category = db.get(self.request.get('ref_category'))
    product.put()