web3.eth.Contract¶
The web3.eth.Contract object makes it easy to interact with smart contracts on the ethereum blockchain.
When you create a new contract object you give it the json interface of the respective smart contract
and web3 will auto convert all calls into low level ABI calls over RPC for you.
This allows you to interact with smart contracts as if they were JavaScript objects.
To use it standalone:
new contract¶
new web3.eth.Contract(jsonInterface[, address][, options])
Creates a new contract instance with all its methods and events defined in its json interface object.
Parameters¶
jsonInterface-Object: The json interface for the contract to instantiateaddress-String(optional): The address of the smart contract to call, can be added later usingmyContract.options.address = '0x1234..'options-Object(optional): The options of the contract. Some are used as fallbacks for calls and transactions:from-String: The address transactions should be made from.gasPrice-String: The gas price in wei to use for transactions.gas-Number: The maximum gas provided for a transaction (gas limit).data-String: The byte code of the contract. Used when the contract gets deployed.
Returns¶
Object: The contract instance with all its methods and events.
Example¶
var myContract = new web3.eth.Contract([...], '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe', {
from: '0x1234567890123456789012345678901234567891', // default from address
gasPrice: '20000000000' // default gas price in wei, 20 gwei in this case
});
= Properties =¶
options¶
myContract.options
The options object for the contract instance. from, gas and gasPrice are used as fallback values when sending transactions.
Properties¶
Object - options:
address-String: The address where the contract is deployed. See options.address.jsonInterface-Array: The json interface of the contract. See options.jsonInterface.data-String: The byte code of the contract. Used when the contract gets deployed.from-String: The address transactions should be made from.gasPrice-String: The gas price in wei to use for transactions.gas-Number: The maximum gas provided for a transaction (gas limit).
Example¶
myContract.options;
> {
address: '0x1234567890123456789012345678901234567891',
jsonInterface: [...],
from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe',
gasPrice: '10000000000000',
gas: 1000000
}
myContract.options.from = '0x1234567890123456789012345678901234567891'; // default from address
myContract.options.gasPrice = '20000000000000'; // default gas price in wei
myContract.options.gas = 5000000; // provide as fallback always 5M gas
options.address¶
myContract.options.address
The address used for this contract instance. All transactions generated by web3.js from this contract will contain this address as the “to”.
The address will be stored in lowercase.
Property¶
address - String|null: The address for this contract, or null if it’s not yet set.
Example¶
myContract.options.address;
> '0xde0b295669a9fd93d5f28d9ec85e40f4cb697bae'
// set a new address
myContract.options.address = '0x1234FFDD...';
options.jsonInterface¶
myContract.options.jsonInterface
The json interface object derived from the ABI of this contract.
Property¶
jsonInterface - Array: The json interface for this contract. Re-setting this will regenerate the methods and events of the contract instance.
Example¶
myContract.options.jsonInterface;
> [{
"type":"function",
"name":"foo",
"inputs": [{"name":"a","type":"uint256"}],
"outputs": [{"name":"b","type":"address"}]
},{
"type":"event",
"name":"Event",
"inputs": [{"name":"a","type":"uint256","indexed":true},{"name":"b","type":"bytes32","indexed":false}],
}]
// set a new interface
myContract.options.jsonInterface = [...];
= Methods =¶
clone¶
myContract.clone()
Clones the current contract instance.
Parameters¶
none
Returns¶
Object: The new contract instance.
Example¶
var contract1 = new eth.Contract(abi, address, {gasPrice: '12345678', from: fromAddress});
var contract2 = contract1.clone();
contract2.options.address = address2;
(contract1.options.address !== contract2.options.address);
> true
deploy¶
myContract.deploy(options)
Call this function to deploy the contract to the blockchain. After successful deployment the promise will resolve with a new contract instance.
Parameters¶
options-Object: The options used for deployment.data-String: The byte code of the contract.arguments-Array(optional): The arguments which get passed to the constructor on deployment.
Returns¶
Object: The transaction object:
Array- arguments: The arguments passed to the method before. They can be changed.Function- send: Will deploy the contract. The promise will resolve with the new contract instance, instead of the receipt!Function- estimateGas: Will estimate the gas used for deploying.Function- encodeABI: Encodes the ABI of the deployment, which is contract data + constructor parameters
For details to the methods see the documentation below.
Example¶
myContract.deploy({
data: '0x12345...',
arguments: [123, 'My String']
})
.send({
from: '0x1234567890123456789012345678901234567891',
gas: 1500000,
gasPrice: '30000000000000'
}, function(error, transactionHash){ ... })
.on('error', function(error){ ... })
.on('transactionHash', function(transactionHash){ ... })
.on('receipt', function(receipt){
console.log(receipt.contractAddress) // contains the new contract address
})
.on('confirmation', function(confirmationNumber, receipt){ ... })
.then(function(newContractInstance){
console.log(newContractInstance.options.address) // instance with the new contract address
});
// When the data is already set as an option to the contract itself
myContract.options.data = '0x12345...';
myContract.deploy({
arguments: [123, 'My String']
})
.send({
from: '0x1234567890123456789012345678901234567891',
gas: 1500000,
gasPrice: '30000000000000'
})
.then(function(newContractInstance){
console.log(newContractInstance.options.address) // instance with the new contract address
});
// Simply encoding
myContract.deploy({
data: '0x12345...',
arguments: [123, 'My String']
})
.encodeABI();
> '0x12345...0000012345678765432'
// Gas estimation
myContract.deploy({
data: '0x12345...',
arguments: [123, 'My String']
})
.estimateGas(function(err, gas){
console.log(gas);
});
methods¶
myContract.methods.myMethod([param1[, param2[, ...]]])
Creates a transaction object for that method, which then can be called, send, estimated.
The methods of this smart contract are available through:
- The name:
myContract.methods.myMethod(123) - The name with parameters:
myContract.methods['myMethod(uint256)'](123) - The signature:
myContract.methods['0x58cf5f10'](123)
This allows calling functions with same name but different parameters from the JavaScript contract object.
Parameters¶
Parameters of any method depend on the smart contracts methods, defined in the JSON interface.
Returns¶
Object: The transaction object:
Array- arguments: The arguments passed to the method before. They can be changed.Function- call: Will call the “constant” method and execute its smart contract method in the EVM without sending a transaction (Can’t alter the smart contract state).Function- send: Will send a transaction to the smart contract and execute its method (Can alter the smart contract state).Function- estimateGas: Will estimate the gas used when the method would be executed on chain.Function- encodeABI: Encodes the ABI for this method. This can be send using a transaction, call the method or passing into another smart contracts method as argument.
For details to the methods see the documentation below.
Example¶
// calling a method
myContract.methods.myMethod(123).call({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'}, function(error, result){
...
});
// or sending and using a promise
myContract.methods.myMethod(123).send({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'})
.then(function(receipt){
// receipt can also be a new contract instance, when coming from a "contract.deploy({...}).send()"
});
// or sending and using the events
myContract.methods.myMethod(123).send({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'})
.on('transactionHash', function(hash){
...
})
.on('receipt', function(receipt){
...
})
.on('confirmation', function(confirmationNumber, receipt){
...
})
.on('error', console.error);
methods.myMethod.call¶
myContract.methods.myMethod([param1[, param2[, ...]]]).call(options[, callback])
Will call a “constant” method and execute its smart contract method in the EVM without sending any transaction. Note calling can not alter the smart contract state.
Parameters¶
options-Object(optional): The options used for calling.from-String(optional): The address the call “transaction” should be made from.gasPrice-String(optional): The gas price in wei to use for this call “transaction”.gas-Number(optional): The maximum gas provided for this call “transaction” (gas limit).
callback-Function(optional): This callback will be fired with the result of the smart contract method execution as the second argument, or with an error object as the first argument.
Returns¶
Promise returns Mixed: The return value(s) of the smart contract method.
If it returns a single value, it’s returned as is. If it has multiple return values they are returned as an object with properties and indices:
Example¶
// using the callback
myContract.methods.myMethod(123).call({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'}, function(error, result){
...
});
// using the promise
myContract.methods.myMethod(123).call({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'})
.then(function(result){
...
});
// MULTI-ARGUMENT RETURN:
// Solidity
contract MyContract {
function myFunction() returns(uint256 myNumber, string myString) {
return (23456, "Hello!%");
}
}
// web3.js
var MyContract = new web3.eth.Contract(abi, address);
MyContract.methods.myFunction().call()
.then(console.log);
> Result {
myNumber: '23456',
myString: 'Hello!%',
0: '23456', // these are here as fallbacks if the name is not know or given
1: 'Hello!%'
}
// SINGLE-ARGUMENT RETURN:
// Solidity
contract MyContract {
function myFunction() returns(string myString) {
return "Hello!%";
}
}
// web3.js
var MyContract = new web3.eth.Contract(abi, address);
MyContract.methods.myFunction().call()
.then(console.log);
> "Hello!%"
methods.myMethod.send¶
myContract.methods.myMethod([param1[, param2[, ...]]]).send(options[, callback])
Will send a transaction to the smart contract and execute its method. Note this can alter the smart contract state.
Parameters¶
options-Object: The options used for sending.from-String: The address the transaction should be sent from.gasPrice-String(optional): The gas price in wei to use for this transaction.gas-Number(optional): The maximum gas provided for this transaction (gas limit).value- ``Number|String|BN|BigNumber``(optional): The value transferred for the transaction in wei.
callback-Function(optional): This callback will be fired first with the “transactionHash”, or with an error object as the first argument.
Returns¶
The callback will return the 32 bytes transaction hash.
PromiEvent: A promise combined event emitter. Will be resolved when the transaction receipt is available, OR if this send() is called from a someContract.deploy(), then the promise will resolve with the new contract instance. Additionally the following events are available:
"transactionHash"returnsString: is fired right after the transaction is sent and a transaction hash is available."receipt"returnsObject: is fired when the transaction receipt is available. Receipts from contracts will have nologsproperty, but instead aneventsproperty with event names as keys and events as properties. See getPastEvents return values for details about the returned event object."confirmation"returnsNumber,Object: is fired for every confirmation up to the 24th confirmation. Receives the confirmation number as the first and the receipt as the second argument. Fired from confirmation 1 on, which is the block where it’s minded."error"returnsError: is fired if an error occurs during sending. If a out of gas error, the second parameter is the receipt.
Example¶
// using the callback
myContract.methods.myMethod(123).send({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'}, function(error, transactionHash){
...
});
// using the promise
myContract.methods.myMethod(123).send({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'})
.then(function(receipt){
// receipt can also be a new contract instance, when coming from a "contract.deploy({...}).send()"
});
// using the event emitter
myContract.methods.myMethod(123).send({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'})
.on('transactionHash', function(hash){
...
})
.on('confirmation', function(confirmationNumber, receipt){
...
})
.on('receipt', function(receipt){
// receipt example
console.log(receipt);
> {
"transactionHash": "0x9fc76417374aa880d4449a1f7f31ec597f00b1f6f3dd2d66f4c9c6c445836d8b",
"transactionIndex": 0,
"blockHash": "0xef95f2f1ed3ca60b048b4bf67cde2195961e0bba6f70bcbea9a2c4e133e34b46",
"blockNumber": 3,
"contractAddress": "0x11f4d0A3c12e86B4b5F39B213F7E19D048276DAe",
"cumulativeGasUsed": 314159,
"gasUsed": 30234,
"events": {
"MyEvent": {
returnValues: {
myIndexedParam: 20,
myOtherIndexedParam: '0x123456789...',
myNonIndexParam: 'My String'
},
raw: {
data: '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385',
topics: ['0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7', '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385']
},
event: 'MyEvent',
signature: '0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7',
logIndex: 0,
transactionIndex: 0,
transactionHash: '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385',
blockHash: '0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7',
blockNumber: 1234,
address: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'
},
"MyOtherEvent": {
...
},
"MyMultipleEvent":[{...}, {...}] // If there are multiple of the same event, they will be in an array
}
}
})
.on('error', console.error); // If there's an out of gas error the second parameter is the receipt.
methods.myMethod.estimateGas¶
myContract.methods.myMethod([param1[, param2[, ...]]]).estimateGas(options[, callback])
Will call estimate the gas a method execution will take when executed in the EVM without. The estimation can differ from the actual gas used when later sending a transaction, as the state of the smart contract can be different at that time.
Parameters¶
options-Object(optional): The options used for calling.from-String(optional): The address the call “transaction” should be made from.gas-Number(optional): The maximum gas provided for this call “transaction” (gas limit). Setting a specific value helps to detect out of gas errors. If all gas is used it will return the same number.value- ``Number|String|BN|BigNumber``(optional): The value transferred for the call “transaction” in wei.
callback-Function(optional): This callback will be fired with the result of the gas estimation as the second argument, or with an error object as the first argument.
Returns¶
Promise returns Number: The gas amount estimated.
Example¶
// using the callback
myContract.methods.myMethod(123).estimateGas({gas: 5000000}, function(error, gasAmount){
if(gasAmount == 5000000)
console.log('Method ran out of gas');
});
// using the promise
myContract.methods.myMethod(123).estimateGas({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'})
.then(function(gasAmount){
...
})
.catch(function(error){
...
});
methods.myMethod.encodeABI¶
myContract.methods.myMethod([param1[, param2[, ...]]]).encodeABI()
Encodes the ABI for this method. This can be used to send a transaction, call a method, or pass it into another smart contracts method as arguments.
Parameters¶
none
Returns¶
String: The encoded ABI byte code to send via a transaction or call.
Example¶
myContract.methods.myMethod(123).encodeABI();
> '0x58cf5f1000000000000000000000000000000000000000000000000000000000000007B'
= Events =¶
once¶
myContract.once(event[, options], callback)
Subscribes to an event and unsubscribes immediately after the first event or error. Will only fire for a single event.
Parameters¶
event-String: The name of the event in the contract, or"allEvents"to get all events.options-Object(optional): The options used for deployment.filter-Object(optional): Lets you filter events by indexed parameters, e.g.{filter: {myNumber: [12,13]}}means all events where “myNumber” is 12 or 13.topics-Array(optional): This allows you to manually set the topics for the event filter. If given the filter property and event signature, (topic[0]) will not be set automatically.
callback-Function: This callback will be fired for the first event as the second argument, or an error as the first argument. See getPastEvents return values for details about the event structure.
Returns¶
undefined
Example¶
myContract.once('MyEvent', {
filter: {myIndexedParam: [20,23], myOtherIndexedParam: '0x123456789...'}, // Using an array means OR: e.g. 20 or 23
fromBlock: 0
}, function(error, event){ console.log(event); });
// event output example
> {
returnValues: {
myIndexedParam: 20,
myOtherIndexedParam: '0x123456789...',
myNonIndexParam: 'My String'
},
raw: {
data: '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385',
topics: ['0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7', '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385']
},
event: 'MyEvent',
signature: '0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7',
logIndex: 0,
transactionIndex: 0,
transactionHash: '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385',
blockHash: '0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7',
blockNumber: 1234,
address: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'
}
events¶
myContract.events.MyEvent([options][, callback])
Subscribe to an event
Parameters¶
options-Object(optional): The options used for deployment.filter-Object(optional): Let you filter events by indexed parameters, e.g.{filter: {myNumber: [12,13]}}means all events where “myNumber” is 12 or 13.fromBlock-Number(optional): The block number from which to get events on.topics-Array(optional): This allows to manually set the topics for the event filter. If given the filter property and event signature, (topic[0]) will not be set automatically.
callback-Function(optional): This callback will be fired for each event as the second argument, or an error as the first argument.
Returns¶
EventEmitter: The event emitter has the following events:
"data"returnsObject: Fires on each incoming event with the event object as argument."changed"returnsObject: Fires on each event which was removed from the blockchain. The event will have the additional property"removed: true"."error"returnsObject: Fires when an error in the subscription occours.
The structure of the returned event Object looks as follows:
event-String: The event name.signature-String|Null: The event signature,nullif it’s an anonymous event.address-String: Address this event originated from.returnValues-Object: The return values coming from the event, e.g.{myVar: 1, myVar2: '0x234...'}.logIndex-Number: Integer of the event index position in the block.transactionIndex-Number: Integer of the transaction’s index position the event was created in.transactionHash32 Bytes -String: Hash of the transaction this event was created in.blockHash32 Bytes -String: Hash of the block this event was created in.nullwhen it’s still pending.blockNumber-Number: The block number this log was created in.nullwhen still pending.raw.data-String: The data containing non-indexed log parameter.raw.topics-Array: An array with max 4 32 Byte topics, topic 1-3 contains indexed parameters of the event.
Example¶
myContract.events.MyEvent({
filter: {myIndexedParam: [20,23], myOtherIndexedParam: '0x123456789...'}, // Using an array means OR: e.g. 20 or 23
fromBlock: 0
}, function(error, event){ console.log(event); })
.on('data', function(event){
console.log(event); // same results as the optional callback above
})
.on('changed', function(event){
// remove event from local database
})
.on('error', console.error);
// event output example
> {
returnValues: {
myIndexedParam: 20,
myOtherIndexedParam: '0x123456789...',
myNonIndexParam: 'My String'
},
raw: {
data: '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385',
topics: ['0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7', '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385']
},
event: 'MyEvent',
signature: '0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7',
logIndex: 0,
transactionIndex: 0,
transactionHash: '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385',
blockHash: '0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7',
blockNumber: 1234,
address: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'
}
events.allEvents¶
myContract.events.allEvents([options][, callback])
Same as events but receives all events from this smart contract. Optionally the filter property can filter those events.
getPastEvents¶
myContract.getPastEvents(event[, options][, callback])
Gets past events for this contract.
Parameters¶
event-String: The name of the event in the contract, or"allEvents"to get all events.options-Object(optional): The options used for deployment.filter-Object(optional): Lets you filter events by indexed parameters, e.g.{filter: {myNumber: [12,13]}}means all events where “myNumber” is 12 or 13.fromBlock-Number(optional): The block number from which to get events on.toBlock-Number(optional): The block number to get events up to (Defaults to"latest").topics-Array(optional): This allows manually setting the topics for the event filter. If given the filter property and event signature, (topic[0]) will not be set automatically.
callback-Function(optional): This callback will be fired with an array of event logs as the second argument, or an error as the first argument.
Returns¶
Promise returns Array: An array with the past event Objects, matching the given event name and filter.
For the structure of a returned event Object see getPastEvents return values.
Example¶
myContract.getPastEvents('MyEvent', {
filter: {myIndexedParam: [20,23], myOtherIndexedParam: '0x123456789...'}, // Using an array means OR: e.g. 20 or 23
fromBlock: 0,
toBlock: 'latest'
}, function(error, events){ console.log(events); })
.then(function(events){
console.log(events) // same results as the optional callback above
});
> [{
returnValues: {
myIndexedParam: 20,
myOtherIndexedParam: '0x123456789...',
myNonIndexParam: 'My String'
},
raw: {
data: '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385',
topics: ['0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7', '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385']
},
event: 'MyEvent',
signature: '0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7',
logIndex: 0,
transactionIndex: 0,
transactionHash: '0x7f9fade1c0d57a7af66ab4ead79fade1c0d57a7af66ab4ead7c2c2eb7b11a91385',
blockHash: '0xfd43ade1c09fade1c0d57a7af66ab4ead7c2c2eb7b11a91ffdd57a7af66ab4ead7',
blockNumber: 1234,
address: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'
},{
...
}]