Blockchain Events

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Blockchain Events
Events being logged by GoodDAPP
Definition
Events are the Solidity abstraction on top of the EVM's logging functionality.
Events are inheritable members of contracts. When you call them, they cause the arguments to be stored in the transaction’s log - a special data structure in the blockchain. These logs are associated with the address of the contract, are incorporated into the blockchain, and stay there as long as a block is accessible. The Log and its event data is not accessible from within contracts.
See: Solidity Official documentation for Events​
How we listen to events
GoodDAPP currently supports subscription to events through polling. Using GoodWallet pollForEvents method, we can listen for logs in an almost real time manner. pollForEvents is periodically polling for events like the specified event (filters by the specified event) up to the current blockchain block, and perform callback on them.
Under the hood, pollForEvents relies on another two methods (getEvents and oneTimeEvents).
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goodWallet.pollForEvents(
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  {
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    event: 'Transfer',
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    contract: goodWalletContract,
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    fromBlock,
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    filterPred: { from: address }
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  },
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  (error, events) => log.debug('send events', { error, events })
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)
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How we parse them
pollForEvents receive a callback which processes the list of events received from the filtered query.
At GoodWallet, the method listenTxUpdates initialize 2 main listeners:
1.For Transfer funds from the account.
2.For Transfer funds to the account.
In both cases, events are polled from the latest block that was not polled before (starting from the block the user was created and advancing). Once these events were filtered (found) by the client:
Their receipts + Logs are being loaded from the Blockchain. The receipts + Logs object of each event are sent to the event subscriber. Subscribers to "transferFrom" are subscribing to receiptUpdated flag, and to "transferTo" are subscribing to receiptReceived flag.
Subscribers to "send" / "recieve" (accordingly) and balanceChanged flags are invoked also.
How they effect the UI
Account balance is updated after a Transfer (from or to) event is processed. As well, entitlement (amount to be claimed) is re-queried and updated accordingly.
All the funds movement between accounts, to/from the current account are listed in the Dashboard's feed list.
Contracts
Contracts being used by GoodDAPP logs different information in the form of events.
The list of contracts that GoodDAPP is aware of:
​GoodDollar.sol​
​GoodDollarReserve.sol​
​Identity.sol​
​OneTimePaymentLinks.sol​
​RedemptionFunctional.sol​
Events by Contract
​GoodDollar​
​PopulatedMarket()​
​Transfer(from, to, value)​
​Transfer(from, to, value, data)​
​TransactionFees(fee, burned)​
​OwnershipTransferred(previousOwner, newOwner)​
​MinterAdded(account)​
​MinterRemoved(account)​
​Approval(owner, spender, value)​
​ContractFallbackCallFailed(from, to, value)​
​GooDollarReserve​
​SignerAdded(account)​
​SignerRemoved(account)​
​OwnershipTransferred(previousOwner, newOwner)​
​Identity​
​WhitelistedAdded(account)​
​WhitelistedRemoved(account)​
​WhitelistAdminAdded(account)​
​WhitelistAdminRemoved(account)​
​OneTimePaymentLinks​
​PaymentDeposit(from, hash, amount)​
​PaymentWithdraw(from, to, hash, amount)​
​OwnershipTransferred(previousOwner, newOwner)​
​PaymentCancel(from, hash, amount)​
​RedemptionFunctional​
​UBIClaimed(by, total)​
​OwnershipTransferred(previousOwner, newOwner)​
GoodDollar
PopulatedMarket()
when: During deployment/migration process, in the G$s minting phase. It's a one-time event.
where: Emitted when the GoodDollar.initialMove() method is called and successfully executed.
Transfer(address indexed from, address indexed to, uint value)
when: Every time a user Sends (Transfers) G$s to an account.
where: In Send flow, user is able to transfer directly to an account by calling GoodDollar.transfer() specifying destination address, email, mobile or username.
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from: who sent the G$
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to: to whom the G$ was sent
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value: the amount of G$ (in wei) being transferred
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Transfer(address indexed from, address indexed to, uint value, bytes data)
when: Every time a user generates a link to share G$s in Send screen.
where: In Send flow, user is able to generate a link to later be withdrawn by calling GoodDollar.transferAndCall().
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from: who sent the G$
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to: to whom the G$ was sent
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value: the amount of G$ (in wei) being transferred
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data: encoded ABI to be called after G$ transfer
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TransactionFees(uint256 fee, uint256 burned)
when: Every time a Transfer is done.
where: In Send flow, user is able to send G$s to another wallet by specifying its address, email, mobile or username, or by generating a link to later be withdrawn by calling GoodDollar.transfer(), GoodDollar.transferAndCall().
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fee: fee being charged for the transaction (in wei).
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     And transferred to the GoodDollarReserve contract.
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burned: fee being charged for the transaction (in wei).
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        And burned if transaction was successfull.
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OwnershipTransferred(address indexed previousOwner, address indexed newOwner)
when: During deployment/migration process.
where: At contract deployment step, previous owner is set to 0x0. And at the end of the migration process, ownership is transferred to the GoodDollarReserve contract.
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previosOwner: address of the previous owner.
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              The one who requested the ownership transfer.
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newOwner: addres of the new owner.
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MinterAdded(address indexed account)
when: During deployment/migration process.
where: At contract deployment, account used to deploy contract is being assigned. During migration GoodDollarReserve contract is also added.
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account: the address of the contract/account who can mint.
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MinterRemoved(address indexed account)
when: During migration process.
where: During migration, after adding GoodDollarReserve, the deployer account is being removed. **
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account: the address of minter to be removed from minters list.
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Approval(address indexed owner, address indexed spender, uint256 value)
when: Not being used.
where: Not being used.
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owner: account that approves an amount of tokens to be spent by the 'spender'.
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spender: account approved to spent an amount of tokens on behalf of the 'owner'.
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value: amount of tokens approved to be spent by the 'spender'.
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ContractFallbackCallFailed(address from, address to, uint256 value)
when: When a transfer of G$s is being made to a contract that don't have onTokenTransfer method.
where: In the ÐApp, when sending directly to an address.
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from: address making the transfer of G$s.
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to: address to where the G$s where sent.
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value: the amount of G$s being transferred.
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GoodDollarReserve
SignerAdded(address indexed account)
when: During deployment process.
where: At deployment step, when class constructor is called.
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account: the address of the contract's signer.
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SignerRemoved(address indexed account)
when: Not being used.
where: Not being used.
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account: the address of the contract's signer to be removed.
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OwnershipTransferred(address indexed previousOwner, address indexed newOwner)
when: During deployment/migration process.
where: At contract deployment step, previous owner is set to 0x0. And at the end of the migration process, ownership is transferred to RedemptionFunctional contract.
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previosOwner: address of the previous owner.
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              The one who requested the ownership transfer.
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newOwner: addres of the new owner.
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Identity
WhitelistedAdded(address indexed account)
when: During migration process. And every time a new user is validated in GoodDAPP.
where: During migration GoodDollar, GoodDollarReserve and OneTimePaymentLinks are added to the list. During application lifetime, when a user has been validated (email, mobile and Face Recognition).
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account: address added to the validated list of GoodDAPP accounts.
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WhitelistedRemoved(address indexed account)
when: Not being used.
where: Not being used.
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account: address removed from the validated list of GoodDAPP accounts.
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WhitelistAdminAdded(address indexed account)
when: During deployment/migration process.
where: At deployment step, when class constructor is called, sets account used to deploy the contract.
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account: address added to the admin list.
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WhitelistAdminRemoved(address indexed account)
when: Not being used.
where: Not being used.
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account: address removed from admin list.
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OneTimePaymentLinks
PaymentDeposit(address indexed from, bytes32 hash, uint256 amount)
when: When a deposit is being made from the ÐApp.
where: In Send flow, if user generates a link to share G$s, the amount specified will generate a deposit to the contract.
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from: account that deposits G$s.
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hash: identifier for the amount being deposited.
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amount: the amount of G$s being deposited.
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PaymentWithdraw(address indexed from, address indexed to, bytes32 indexed hash, uint256 amount)
when: When a withdraw is being made from the ÐApp.
where: Accessing the withdraw link being generated by Send -> Generate Link. Or by scanning, in the Receive flow, the QR code generated from the Sender
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from: address that generated the deposit to be withdrawn.
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to: address that excecuted the withdraw.
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hash: identifier for the amount being withdrawn.
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amount: the mount of G$s being withdrawn.
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OwnershipTransferred(address indexed previousOwner, address indexed newOwner)
when: During deployment process.
where: At deployment, ownership is transferred to the deployer account.
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previosOwner: address of the previous owner.
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              The one who requested the ownership transfer.
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newOwner: addres of the new owner.
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PaymentCancel(address indexed from, bytes32 hash, uint256 amount)
when: When a user that generates the deposit decides to cancel it.
where: Not being used.
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from: address that cancels the deposit.
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hash: identifier for the deposit.
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amount: amount being cancelled.
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RedemptionFunctional
UBIClaimed(address indexed by, uint256 total)
when: When user claims its G$s.
where: In the ÐApp, when user has G$s to claim, it can go to the Claim flow and receive the G$s after making a Face Recognition validation.
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by: registered address that claims G$s tokens.
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total: amount of G$s being claimed.
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OwnershipTransferred(address indexed previousOwner, address indexed newOwner)
when: During deployment process.
where: At deployment, ownership is transferred to the deployer account.
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previosOwner: address of the previous owner.
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              The one who requested the ownership transfer.
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newOwner: addres of the new owner.
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Contents
Definition
How we listen to events
How we parse them
How they effect the UI