A dart library that connects to interact with the Ethereum blockchain. It connects to an Ethereum node to send transactions, interact with smart contracts and much more!
- Connect to an Ethereum node with the rpc-api, call common methods
- Send signed Ethereum transactions
- Generate private keys, setup new Ethereum addresses
- Call functions on smart contracts and listen for contract events
- Code generation based on smart contract ABI for easier interaction
- Encode all supported solidity types, although only (u)fixed, which are not commonly used, are not supported at the moment.
Credentials and Wallets #
In order to send transactions on the Ethereum network, some credentials are required. The library supports raw private keys and v3 wallet files.
import 'dart:math'; //used for the random number generator import 'package:web3dart/web3dart.dart'; // You can create Credentials from private keys Credentials fromHex = EthPrivateKey.fromHex("c87509a[...]dc0d3"); // Or generate a new key randomly var rng = new Random.secure(); Credentials random = EthPrivateKey.createRandom(random)(rng); // In either way, the library can derive the public key and the address // from a private key: var address = await credentials.extractAddress(); print(address.hex);
Another way to obtain
Credentials which the library uses to sign
transactions is the usage of a wallet file. Wallets store a private
key securely and require a password to unlock. The library has experimental
support for version 3 wallets commonly generated by other Ethereum clients:
import 'dart:io'; import 'package:web3dart/web3dart.dart'; String content = new File("wallet.json").readAsStringSync(); Wallet wallet = Wallet.fromJson(content, "testpassword"); Credentials unlocked = wallet.privateKey; // You can now use these credentials to sign transactions or messages
You can also create Wallet files with this library. To do so, you first need the private key you want to encrypt and a desired password. Then, create your wallet with
Wallet wallet = Wallet.createNew(credentials, "password", random); print(wallet.toJson());
You can also write
wallet.toJson() into a file which you can later open
(select Keystore / JSON File) or other Ethereum clients like geth.
If you want to integrate
web3dart with other wallet providers, you can implement
Credentials and override the appropriate methods.
Connecting to an RPC server #
The library won't send signed transactions to miners itself. Instead, it relies on an RPC client to do that. You can use a public RPC API like infura, setup your own using geth or, if you just want to test things out, use a private testnet with truffle and ganache. All these options will give you an RPC endpoint to which the library can connect.
import 'package:http/http.dart'; //You can also import the browser version import 'package:web3dart/web3dart.dart'; var apiUrl = "http://localhost:7545"; //Replace with your API var httpClient = new Client(); var ethClient = new Web3Client(apiUrl, httpClient); var credentials = ethClient.credentialsFromPrivateKey("0x..."); // You can now call rpc methods. This one will query the amount of Ether you own EtherAmount balance = ethClient.getBalance(credentials.address); print(balance.getValueInUnit(EtherUnit.ether));
Sending transactions #
Of course, this library supports creating, signing and sending Ethereum transactions:
import 'package:web3dart/web3dart.dart'; /// [...], you need to specify the url and your client, see example above var ethClient = new Web3Client(apiUrl, httpClient); var credentials = ethClient.credentialsFromPrivateKey("0x..."); await client.sendTransaction( credentials, Transaction( to: EthereumAddress.fromHex('0xC91...3706'), gasPrice: EtherAmount.inWei(BigInt.one), maxGas: 100000, value: EtherAmount.fromUnitAndValue(EtherUnit.ether, 1), ), );
Missing data, like the gas price, the sender and a transaction nonce will be
obtained from the connected node when not explicitly specified. If you only need
the signed transaction but don't intend to send it, you can use
Smart contracts #
The library can parse the abi of a smart contract and send data to it. It can also listen for events emitted by smart contracts. See this file for an example.
Feature requests and bugs #
Please file feature requests and bugs at the issue tracker. If you want to contribute to this libary, please submit a Pull Request.
- include a
0xfor hex data in
eth_estimateGas- thanks, @Botary
- Fixed a bug when decoding negative integers (#73)
Web3Clientto estimate the amount of gas that would be used by a transaction.
In 1.2.1, the
atBlock parameter on
estimateGas was deprecated and will be ignored.
1.1.1, 1.1.1+1 #
- Fix parsing transaction receipts when the block number is not yet available. Thanks to @chart21 for the fix.
- Fix a typo that made it impossible to load the coinbase address. Thanks to @modulovalue for the fix.
getTransactionReceiptto get more detailed information about a transaction, including whether it was executed successfully or not.
Basically a complete rewrite of the library - countless bug fixes, a more fluent and consistent api and more features:
- experimental api to perform expensive operations in a background isolate. Set
enableBackgroundIsolateto true when creating a
Web3Clientto try it out.
- Events! Use
eventsfor auto-updating streams.
- The client now has a
dispose()method which should be called to stop the background isolate and terminate all running streams.
This version contains breaking changes! Here is an overview listing some of them.
|Creating credentials via ||Use the |
|Sending transactions or calling contract functions||The api has been changed to just a single methods instead of a transaction builder. See the examples for details.|
|Low-level cryptographic operations like signing, hashing and converting hex <-> byte array <-> integer||Not available in the core library. Import |
If you run into problems after updating, please create an issue.
getTransactionByHashmethod - thank you, maxholman!
- Allow a different N parameter for scrypt when creating new wallets.
- New APIs allowing for a simpler access to wallets, credentials and addresses
- More examples in the README
- More solidity types, not with encoding.
- Send transactions and call messages from smart contracts on the Blockchain.
- Create new Ethereum accounts
- Send and sign transactions
- Initial version, created by Stagehand
Use this package as a library
1. Depend on it
Add this to your package's pubspec.yaml file:
dependencies: web3dart: ^1.2.3
2. Install it
You can install packages from the command line:
$ pub get
$ flutter pub get
Alternatively, your editor might support
pub get or
flutter pub get.
Check the docs for your editor to learn more.
3. Import it
Now in your Dart code, you can use:
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Code health derived from static analysis. [more]
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We analyzed this package on Apr 7, 2020, and provided a score, details, and suggestions below. Analysis was completed with status completed using:
- Dart: 2.7.1
- pana: 0.13.6
lib/src/contracts/abi/abi.dart. (-1.49 points)
lib/src/contracts/abi/abi.dart reported 3 hints:
line 143 col 9: DO use curly braces for all flow control structures.
line 145 col 9: DO use curly braces for all flow control structures.
line 222 col 7: DO use curly braces for all flow control structures.
lib/src/core/sync_information.dart. (-1 points)
lib/src/core/sync_information.dart reported 2 hints:
line 26 col 7: DO use curly braces for all flow control structures.
line 28 col 7: DO use curly braces for all flow control structures.
lib/src/contracts/abi/arrays.dart. (-0.50 points)
lib/src/contracts/abi/arrays.dart reported 1 hint:
line 141 col 7: DO use curly braces for all flow control structures.
Fix additional 3 files with analysis or formatting issues. (-1.50 points)
Additional issues in the following files:
Maintain an example.
None of the files in the package's
example/ directory matches known example patterns.
Common filename patterns include
web3dart.dart. Packages with multiple examples should provide
For more information see the pub package layout conventions.
|Dart SDK||>=2.2.2 <3.0.0|