Consumer Crypto

So, you're thinking of adding fiat payments to your dapp? Let's say you don't want to depend on too many third-party providers and want to build the solution in-house.

Here's how you'd do it 👇

Building paywithglide.xyz. ex Robinhood, Uber, Apple

1. Setup a "hot" wallet that holds funds to sponsor the transactions on behalf of the user.

If you are executing transactions on multiple chains, you need to have a wallet setup on every chain. Ditto for tokens - if you're contract spends a variety of tokens, your wallets need to hold balance for all of them.

2. Ideally, setup some sort of balance monitoring so if the wallet balance goes too low, you get notified immediately and you can replenish it.

Anyways, onto the fiat part.

4. Once you collect the fiat payment from the user, your payment processor will notify you. This can be a callback or a webhook. Stripe recommends using webhooks for this.

5. In your webhook, you can now run the onchain transaction using the wallet we setup earlier. Your contract would need to support "sponsored" transactions and not depend on "msg.sender". Otherwise, your hot wallet will end up getting the onchain assets!

6. That's it. You should have a working solution. But, there's lots of pitfalls here. I'll post a thread later with important things to know.

3. Find a payment processor. This can be Stripe or Apple's IAP if you're building a mobile app.

To collect payment from the user, you need to calculate the dollar value of each transaction. Use a market data api like coingecko and calculate the price of your tx. Don't forget to include payment processing fees!