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Fungible Token Drops

Time to level up! Let's add support for fungible token drops. This is where things get interesting because we need to interact with other contracts.

Why FT Drops Are Different​

Unlike NEAR tokens (which are native), fungible tokens live in separate contracts. This means:

  • Cross-contract calls to transfer tokens
  • User registration on FT contracts (for storage)
  • Callback handling when things go wrong
  • More complex gas management

But don't worry - we'll handle all of this step by step.

Extend Drop Types​

First, let's add FT support to our drop types in src/drop_types.rs:

Update the helper methods:

Cross-Contract Interface​

Create src/external.rs to define how we talk to FT contracts:

Creating FT Drops​

Add this to your main contract in src/lib.rs:

FT Claiming Logic​

The tricky part! Update your src/claim.rs:

FT claiming with automatic user registration:

Testing FT Drops​

You'll need an FT contract to test with. Let's use a simple one:

# Deploy a test FT contract (you can use the reference implementation)
near create-account test-ft.testnet --useFaucet
near deploy test-ft.testnet ft-contract.wasm

# Initialize with your drop contract as owner
near call test-ft.testnet new_default_meta '{
  "owner_id": "drop-test.testnet",
  "total_supply": "1000000000000000000000000000"
}' --accountId test-ft.testnet

Register your drop contract and transfer some tokens to it:

# Register drop contract
near call test-ft.testnet storage_deposit '{
  "account_id": "drop-test.testnet"
}' --accountId drop-test.testnet --deposit 0.25

# Transfer tokens to drop contract
near call test-ft.testnet ft_transfer '{
  "receiver_id": "drop-test.testnet",
  "amount": "10000000000000000000000000"
}' --accountId drop-test.testnet --depositYocto 1

Now create an FT drop:

# Create FT drop with 1000 tokens per claim
near call drop-test.testnet create_ft_drop '{
  "public_keys": [
    "ed25519:HcwvxZXSCX341Pe4vo9FLTzoRab9N8MWGZ2isxZjk1b8"
  ],
  "ft_contract": "test-ft.testnet",
  "amount_per_drop": "1000000000000000000000000"
}' --accountId drop-test.testnet --deposit 2

Claim the FT drop:

# Claim FT tokens (recipient gets registered automatically)
near call drop-test.testnet claim_for '{
  "account_id": "alice.testnet"
}' --accountId drop-test.testnet \
  --keyPair <private-key-here>

# Check if Alice received the tokens
near view test-ft.testnet ft_balance_of '{"account_id": "alice.testnet"}'

Add Helper Functions​

Common Issues & Solutions​

"Storage deposit failed"

  • The FT contract needs sufficient balance to register users
  • Make sure you attach enough NEAR when creating the drop

"FT transfer failed"

  • Check that the drop contract actually owns the FT tokens
  • Verify the FT contract address is correct

"Gas limit exceeded"

  • FT operations use more gas than NEAR transfers
  • Our gas constants should work for most cases

What You've Accomplished​

Great work! You now have:

✅ FT drop creation with cost calculation ✅ Cross-contract calls to FT contracts
✅ Automatic user registration on FT contracts ✅ Callback handling for robust error recovery ✅ Gas optimization for complex operations

FT drops are significantly more complex than NEAR drops because they involve multiple contracts and asynchronous operations. But you've handled it like a pro!

Next up: NFT drops, which have their own unique challenges around uniqueness and ownership.

Continue to NFT Drops →

Pro Tip

Always test FT drops with small amounts first. The cross-contract call flow has more moving parts, so it's good to verify everything works before creating large drops.