Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>This is documented <a href="http://code.google.com/appengine/docs/python/datastore/expandoclass.html" rel="nofollow">here</a>. The snippet provided is valid, although it's not clear why the class is completely empty (might be for illustrational purposes). I suppose the main question is <em>when to use Expando Model</em>? </p> <p>Imagine a site collecting orders for all kinds of goods possible. One customer might want to order a kitten, another one might want to order a book, etc. A books and a kitten have very little in common, maybe just a price and weight. But we want our customers to provide details on their irders, e.g. one customer might order a kitten 3 months old, siamese, blue eyed, and another might order "Lord of The Rings" 2nd edition, hardcover, author signed, etc. Although these properties aren't relevant at the moment of collecting an order, they are vital of your business logic. Also you might process these properties later. </p> <p>The only solution here is to use Expando model, because you can't create a universal class (or hierarchy of classes) covering all the existing properties. The Expando model will hold all the general properties (price, weight, tracking id, shipping cost, custom fees, etc.) and methods (calculating total, discounts, etc.), the rest of the properties will be created by the customer dynamically at runtime. A model instance will be saved into the datastore with all its properties, and any particular instance will return all the properties defined on it via Model.properties() method. </p>
    singulars
    1. This table or related slice is empty.
    1. PODefining attributes for objects/entities in python/google app engine
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USeGlyph
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PODefining attributes for objects/entities in python/google app engine
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COThat was a very clear and short explanation, if only the author bothered to do that.
      singulars
      1. PO
      1. USshafty
    2. COGood explanation, though I would argue not a great reason: if these properties are essential to your business logic, they should be included in the model definition somewhere.
      singulars
      1. PO
      1. USNick Johnson
    3. CONot really necessary. These properties are essential for fulfilling a customer's request (like the customer gets red coffee mug, not blue), they have little value from processing logic. Do you think it would be a misuse of Expando? What would be a better way, given that I don't know in advance neither the quantity of properties on a particular instance nor their type?
      singulars
      1. PO
      1. USeGlyph
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload