Token Transfer

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Token Transfer

Acala supports different types of tokens than Polkadot, and allows various ways to transfer tokens. This guide will walk through tokens available on Acala, tools can be used for transfers, how to send transfer transactions, monitor and track these transactions.
Token Types
Token
Symbol
Description
CurrencyId
Decimals
Minimal Balance
ACA
native token of Acala network
Token(ACA)
12
0.1 ACA
aUSD
multi-collateralized stablecoin
Token(AUSD)
12
0.1 aUSD
DOT
crossed to Acala from Polkadot Relay Chain
Token(DOT)
10
0.01 DOT
LDOT
tokenized staked DOT from the Liquid Staking protocol
Token(LDOT)
10
0.05 LDOT
AssetRegistry registered the metadata info of this type token.
DexShare
The lp share token for the trading pair of Acala DEX. The CurrencyId type of Acala DEX's lp token are CurrencyId::DexShare, and the decimals and minimal balance of lp token are same as the first token in DexShare. For example, CurrencyId::DexShare(Token(ACA), Token(AUSD)) is the CurrencyId of lp token of ACA/aUSD pair, its decimal is 12, and minimal balance is 0.1, these are same as ACA.
Currently, AssetRegistry does not register metadata info of any lp token.
Erc20
Token issued by ERC20 contracts deployed in Acala EVM+. The CurrencyId type is Erc20(Address), Address is the ERC20 contract address on EVM+.
LiquidCrowdloan
Symbol
Description
CurrencyId
Decimals
Minimal Balance
LcDOT
tokenized liquid receipt of crowdloaned DOT
LiquidCrowdloan(13)
10
0.01 LcDOT
AssetRegistry registered the metadata info of this type token.
ForeignAsset
Tokens originated from other parachains.
AssetRegistry registered the metadata info of this type token.
Query token's metadata on assetRegistry
query asset metadata
Tools
JS/TS SDK: https://github.com/AcalaNetwork/acala.js​
Blockchain explorer: http://acala.subscan.io​
api-sidecar: https://github.com/paritytech/substrate-api-sidecar​
txwrapper: https://github.com/AcalaNetwork/txwrapper​
SubQuery: https://github.com/AcalaNetwork/acala-subql​
Token balances
Query chain state to get token balances.
Native token (ACA) balances
Query system module to get native token (ACA) balances data.
system.account
Returns the AccountInfo of given account. For different types of balances, check the fields in AccountInfo.data
free: the free balance.
reserve: the reserved balance.
Other tokens
For non-native tokens, like DOT, LDOT, aUSD, query tokens module to get balances info.
tokens.accounts
Returns the OrmlAccountData of given account and currency ID. For different types of balances, check the fields:
free: the free balance.
reserved: the reserved balance.
tokens.lock
Returns the BalanceLock of given account and currency ID. BalanceLock has two fields:
id: the lock identifier.
amount. the locked amount.
Note locks could be overlapped, and the same amount of tokens could be under locked by multiple locks.
Send Tokens
Transactions
currencies.transfer
​https://acala.subscan.io/extrinsic?module=Currencies&call=transfer​
This can be used to send any supported tokens in the network, including ACA, DOT, LDOT, LCDOT, aUSD etc.
currencies.transferNativeCurrency
​https://acala.subscan.io/extrinsic?module=Currencies&call=transfer_native_currency​
This can be used to send native token (ACA). It has slightly cheaper transaction fees compare to currencies.transfer
balances.transfer
​https://acala.subscan.io/extrinsic?module=Balances&call=transfer​
Same as currencies.transferNativeCurrency, only for native token (ACA).
Compatible with Polkadot / Polkadot and most other Substrate-based chains.
Receive Tokens
There are multiple ways to detect incoming balance transfers:
Monitor events
Subscribe storage changes
Monitor transactions
Monitor Events
Monitoring events is a recommended way to track incoming balance transfers. It can handle ALL types of transfer transactions including the one that is not initiated by a transaction directly (e.g. delayed proxy).
balances.transfer
​https://acala.subscan.io/event?module=Balances&event=Transfer​
Emitted when a native token (ACA) transfer happened.
currencies.transfer
​https://acala.subscan.io/event?module=Currencies&event=Transferred​
Emitted when a token transfer happened.
NOTE: This is not emitted when balances.transfer is used to make a transfer.
currencies.deposit
​https://acala.subscan.io/event?module=Currencies&event=Deposited​
Emitted when a token is minted to an account. This could happen when it is a cross-chain transfer or it is a transaction minting stablecoins.
For cross-chain transfer, there would be ExecutedDownward event along with the deposit. https://acala.subscan.io/event?address=&module=dmpqueue&event=executeddownward​
xtokens.transferred
​https://acala.subscan.io/event?address=&module=xtokens&event=transferred​
Emitted when a cross-chain transfer happened from Acala to other chains.
Triggered by xtokens.transfer extrinsic.
xtokens.transferredmultiasset
​https://acala.subscan.io/event?address=&module=xtokens&event=transferredmultiasset​
Emitted when a cross-chain transfer happened from Acala to other chains.
Triggered by xtokens.transfer_multiasset extrinsic.
Storage changes RPC
​state_subscribeStorage​
Subscribe to a list of account balances. However, it does not guarantee subscription delivery due to connection errors or blockchain reorg.
Monitor Transactions
It is possible to fetch transactions in every block, check for transfer transactions, and check if the transfer transaction is successful. However, this may likely yield false-negative results i.e. deposit received but failed to recognize, due to the various ways for transfer.
Refer to Send Tokens section for direct transfer transactions. In additional, to sending transfer transactions individually, there are common utility methods to batch send transfer transactions:
utility.batch
​https://acala.subscan.io/extrinsic?module=Utility&call=batch​
This can be used to send batch transaction
NOTE: batched transactions will always emit success events.
utility.BatchCompleted event indicates that all transactions are successful
utility.BatchInterrupted event indicates which transaction failed. Transactions before the failed transaction are executed successfully and will not be reverted.
utility.batchAll
​https://acala.subscan.io/extrinsic?module=Utility&call=batch_all​
This is similar to utility.batch but will revert all transactions upon failed transaction.
​Transfer Code Samples​