django - Database structure to handle similar/same object at varying business levels -

-

scenario

a well-known taco establishment wants build django app models combo, comboitem, ingredient, , order.

  1. headquarters wants create various combos included items , layout original item ingredients , price.
  2. each franchise can select combos sell on menu , allowed adjust price , ingredients of combo items store.
  3. when order comes in, combo , item details should show on log , should not change in future if hq renames combo or franchise changes price/ingredients.

use case

  1. hq creates "hot taco combo". has 3 related combo items

    • a taco (price: $.99, ingredients: shell, beef, cheese, hot sauce)
    • churro-spirals (price: $.79)
    • drink (price: $1.29)

  2. the ny franchise adds hot taco combo menu. adjust price of taco $1.49 , add lettuce taco.

  3. a customer orders combo no cheese on taco.

  4. hq changes name of combo fiery taco combo - ny's combo name updates taco remains same custom price , still includes lettuce.

  5. a manager @ ny franchise views orders , see's 1 order hot taco combo , taco ingredients shell, meat, , lettuce.

issue

i'm struggling decide best way handle because combo same object @ 3 levels, related comboitem objects can different. hq should able update combo attributes name , update franchise combo names, combo item customizations should remain. additionally, combo details , customizations @ point of sale should never change once recorded, accurate order records.

originally thought have abstractbaseclass each of related models , objects inherit them @ each business level, structure feels redundant , difficult maintain.

then thought use genericforeignkey relate combo either hq, franchise, or order , duplicate objects necessary move down levels. feels weird , error prone.

has dealt case or have recommendations? matter of being complex problem , needing complex solution or there simple approach i'm missing? thank in advance.

it sounds rather abstract base classes, you're looking use multi-table inheritance: https://docs.djangoproject.com/en/1.8/topics/db/models/#multi-table-inheritance

i'd recommend reading through whole section of docs see options inheritance styles: https://docs.djangoproject.com/en/1.8/topics/db/models/#model-inheritance


Comments

Post a Comment

Popular posts from this blog

php - Zend Framework / Skeleton-Application / Composer install issue -

-
i trying create zend framework application using skeleton in netbeans. when run composer install, following error message: "c:\php\php.exe" "c:\composer\composer.phar" "--ansi" "--no-interaction" "update" "--dev" using deprecated option "dev". dev packages installed default now. loading composer repositories package information updating dependencies (including require-dev) requirements not resolved installable set of packages. problem 1 - package requires php >=5.5 php version (5.4.42) not satisfy requirement. problem 2 - installation request zendframework/zendframework 2.5.1 -> satisfiable zendframework/zendframework[2.5.1]. - zendframework/zendframework 2.5.1 requires php >=5.5 -> php version (5.4.42) not satisfy requirement. done. apparently, zend framework only needs php 5.3+ contradicts above. need use php 5.4. my composer.json following: { "name": "
Read more

c# - Better 64-bit byte array hash -

-
i need hash algorithm produces 64-bit hash code ( long ) fewer collisions string.gethashcode() , fast (no expensive calls cryptographic functions). here's implementation of fnv still shows 3% of collisions after testing 2 million random strings. need number way lower. void main() { const string chars = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz!#@$%^&*()_+}{\":?><,./;'[]0123456789\\"; const int n = 2000000; var random = new random(); var hashes = new hashset<long>(); int collisions = 0; for(int = 0; < n; i++) { var len = random.next(chars.length); var str = new char[len]; (int j = 0; j < len; j++) { str[j] = chars[random.next(chars.length)]; } var s = new string(str); if(!hashes.add(get64bithash( s ))) collisions++; } console.writeline("collision percentage after " + n + " random strings: " + ((doubl
Read more

python - PyCharm Type error Message -

-
i'm newbie trying out ml/dbn in python (3.4) under pycharm (comm.ed 4.5). following definition def make_thetas(xmin,xmax,n): xs = np.linespace(xmin,xmax,n) widths = (xs[1:] - xs[:-1])/2.0 thetas = xs[:-1] + widths return thetas throws error "class 'tuple' not define ' sub ', '-' operator cannot used on instance" on - operator on third line (widths = ....) ideas on how code running under pycharm - works alright in interactive python window. thx. to all, after g'g lot have found workaround seems work within pycharm. workaround because (even python newbie) expected python not need explicit typecasting, not when using datatypes imported lib such numpy. def make_thetas(xmin,xmax,n): xs = np.array(np.linspace(xmin,xmax,n)) widths = (xs[1:] - xs[:-1])/2.0 thetas = xs[:-1]+ widths return thetas using docstrings type-hinting such below did not work def make_thetas(xmin,xmax,n): "&q
Read more