Money Exchange
A small React and TypeScript demo for a hackathon: every participant receives a private account, claims a public nickname, and transfers money to other named participants in real time.
The example demonstrates:
- Private identity-owned accounts and an automatic starter balance
- Atomic transfers implemented as a SpacetimeDB reducer
- Private account changes represented as credit and debit entries
- A public recipient directory without exposing other users' balances
Run The Template
Create and run the app with the SpacetimeDB CLI:
spacetime dev --template money-exchange-react-ts Open http://localhost:5173, then open a second private browser window to create another identity and send payments between the two users.
Explore The Code
The server module is in spacetimedb/src/index.ts. On first connection it
creates a private account containing $100.00. Users must claim a unique
nickname before they appear in the recipient directory.
The transfer reducer accepts a recipient identity and a cent amount. It
validates ownership and available funds, debits the sender, credits the
recipient, and writes a Debit account change for the sender and a Credit
account change for the recipient in one transaction. Errors abort the whole
transaction, so a failed payment never partially changes balances or history.
The account and account_change tables are private. The my_account and
my_account_changes views let each connected identity subscribe only to its
own balance and change history. The public directory table contains names
and identities for choosing whom to pay.
The React client is in src/App.tsx; generated type-safe bindings live in
src/module_bindings.
Extend It
This example uses play money. Natural hackathon extensions include payment memos, payment requests, shared wallets, an administrator faucet, or authenticated user profiles.