Charge a dynamic amount of ERC20 for gas payment

Learn how to charge dynamic amount of ERC20 tokens to pay for gas fees.

Charging (any) ERC-20 tokens you want as a form of payment for transactions (also supports stablecoins like USDC).

What you'll learn:#

How to charge ERC20 tokens to users to make a minting NFT transaction.

Select the contract you want to interact with

Add the collectible's smart contract.
Define the smart contract function you want to use. In our case 'mint'.

command-line

curl https://api.openfort.xyz/v1/contracts \
  -u "$YOUR_SECRET_KEY:" \
  -d 'name=NFT Contract' \
  -d 'chainId=80002' \
  -d 'address=contract address'

Set up a Dynamic ERC20 Policy

Create s new policy and select the strategy "charge dynamic amount of ERC20".
Select the ERC20 Token Contract and the Exchange Rate.
Select imported contract and the function you want to sponsor.

If you want to update the dynamic rate programmatically, contact us

command-line

curl https://api.openfort.xyz/v1/policies \
  -u "$YOUR_SECRET_KEY:" \
  -d 'name=My Policy' \
  -d 'chainId=80002' \
  -d 'strategy[sponsorSchema]=charge_custom_rate' \
  -d 'strategy[tokenContract]=con_...' \
  -d 'strategy[tokenContractAmount]=1'

command-line

curl https://api.openfort.xyz/v1/policies/:id/policy_rules \
  -H "Authorization: Bearer $YOUR_SECRET_KEY" \
  -d type="contract_functions" \
  -d functionName="All functions" \
  -d contract="con_..."

Create a gasless transaction

Add chainId
Add contract
Add policy
Add function you want to interact with

Note you can make a transaction happen without the need to have a registered user or account deployed at the time of interacting. Once you make the transaction a playerId and accountId will be created.

command-line

  curl https://api.openfort.xyz/v1/transaction_intents \
  -u "$YOUR_SECRET_KEY:" \
  -d 'chainId=80002' \
  -d 'optimistic=true' \
  -d 'policy=pol_...'
  -d 'interactions[0][contract]=con_...' \
  -d 'interactions[0][functionName]=mint' \
  -d 'interactions[0][functionArgs][0]=sender address or Id'

Optional: Add the Account or Player you're using

Add account or add player

command-line

  curl https://api.openfort.xyz/v1/transaction_intents \
  -u "$YOUR_SECRET_KEY:" \
  -d 'chainId=80002' \
  -d 'policy=pol_...' \
  -d 'account=acc...' or 'player=pla...' \
  -d 'optimistic=true' \
  -d 'interactions[0][contract]=con_...' \
  -d 'interactions[0][functionName]=mint' \
  -d 'interactions[0][functionArgs][0]=sender address or Id'