A simple wallet django application
A wallet is owned by a user. Should you be using a custom user model, the wallet should still work properly as it the wallet points to settings.AUTH_USER_MODEL.
from wallet.models import Wallet
# wallets are owned by users.
wallet = user.wallet_set.create()from django.db import transaction
with transaction.atomic():
# We need to lock the wallet first so that we're sure
# that nobody modifies the wallet at the same time
# we're modifying it.
wallet = Wallet.select_for_update().get(pk=wallet.id)
wallet.deposit(100) # amountfrom django.db import transaction
with transaction.atomic():
# We need to lock the wallet first so that we're sure
# that nobody modifies the wallet at the same time
# we're modifying it.
wallet = Wallet.select_for_update().get(pk=wallet.id)
wallet.withdraw(100) # amountWhen a user tries to withdraw from a wallet with an amount greater than its balance, the transaction raises a wallet.errors.InsufficientBalance error.
# wallet.current_balance # 50
# This raises an wallet.errors.InsufficentBalance.
wallet.withdraw(100)This error inherits from django.db.IntegrityError so that when it is raised, the whole transaction is automatically rolled-back.
One can transfer a values between wallets. It uses withdraw and deposit internally. Should the sending wallet have an insufficient balance, wallet.errors.InsufficientBalance is raised.
with transaction.atomic():
wallet = Wallet.select_for_update().get(pk=wallet_id)
transfer_to_wallet = Wallet.select_for_update().get(pk=transfer_to_wallet_id)
wallet.transfer(transfer_to_wallet, 100)The CURRENCY_STORE_FIELD is a django field class that contains how the fields should be stored. By default, it uses django.models.BigIntegerField. It was chosen that way for simplicity - just make cents into your smallest unit (0.01 -> 1, 1.00 -> 100).
You can change this to decimal by adding this to your settings.py:
# settings.py
CURRENCY_STORE_FIELD = models.DecimalField(max_digits=10, decimal_places=2)You need to run ./manage.py makemigrations after that.
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