Struct ethers::contract::Contract [−][src]
pub struct Contract<M> { /* fields omitted */ }
Expand description
A Contract is an abstraction of an executable program on the Ethereum Blockchain. It has code (called byte code) as well as allocated long-term memory (called storage). Every deployed Contract has an address, which is used to connect to it so that it may be sent messages to call its methods.
A Contract can emit Events, which can be efficiently observed by applications to be notified when a contract has performed specific operation.
There are two types of methods that can be called on a Contract:
-
A Constant method may not add, remove or change any data in the storage, nor log any events, and may only call Constant methods on other contracts. These methods are free (no Ether is required) to call. The result from them may also be returned to the caller. Constant methods are marked as
pure
andview
in Solidity. -
A Non-Constant method requires a fee (in Ether) to be paid, but may perform any state-changing operation desired, log events, send ether and call Non-Constant methods on other Contracts. These methods cannot return their result to the caller. These methods must be triggered by a transaction, sent by an Externally Owned Account (EOA) either directly or indirectly (i.e. called from another contract), and are required to be mined before the effects are present. Therefore, the duration required for these operations can vary widely, and depend on the transaction gas price, network congestion and miner priority heuristics.
The Contract API provides simple way to connect to a Contract and call its methods, as functions on a Rust struct, handling all the binary protocol conversion, internal name mangling and topic construction. This allows a Contract object to be used like any standard Rust struct, without having to worry about the low-level details of the Ethereum Virtual Machine or Blockchain.
The Contract definition (called an Application Binary Interface, or ABI) must
be provided to instantiate a contract and the available methods and events will
be made available to call by providing their name as a str
via the method
and event
methods. If non-existing names are given, the function/event call
will fail.
Alternatively, you can and should use the abigen
macro, or the Abigen
builder
to generate type-safe bindings to your contracts.
Example
Assuming we already have our contract deployed at address
, we’ll proceed to
interact with its methods and retrieve raw logs it has emitted.
use ethers_core::{
abi::Abi,
types::{Address, H256},
};
use ethers_contract::Contract;
use ethers_providers::{Provider, Http};
use ethers_signers::Wallet;
use std::convert::TryFrom;
// this is a fake address used just for this example
let address = "eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee".parse::<Address>()?;
// (ugly way to write the ABI inline, you can otherwise read it from a file)
let abi: Abi = serde_json::from_str(r#"[{"inputs":[{"internalType":"string","name":"value","type":"string"}],"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"author","type":"address"},{"indexed":true,"internalType":"address","name":"oldAuthor","type":"address"},{"indexed":false,"internalType":"string","name":"oldValue","type":"string"},{"indexed":false,"internalType":"string","name":"newValue","type":"string"}],"name":"ValueChanged","type":"event"},{"inputs":[],"name":"getValue","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"lastSender","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"string","name":"value","type":"string"}],"name":"setValue","outputs":[],"stateMutability":"nonpayable","type":"function"}]"#)?;
// connect to the network
let client = Provider::<Http>::try_from("http://localhost:8545").unwrap();
// create the contract object at the address
let contract = Contract::new(address, abi, client);
// Calling constant methods is done by calling `call()` on the method builder.
// (if the function takes no arguments, then you must use `()` as the argument)
let init_value: String = contract
.method::<_, String>("getValue", ())?
.call()
.await?;
// Non-constant methods are executed via the `send()` call on the method builder.
let call = contract
.method::<_, H256>("setValue", "hi".to_owned())?;
let pending_tx = call.send().await?;
// `await`ing on the pending transaction resolves to a transaction receipt
let receipt = pending_tx.confirmations(6).await?;
Event Logging
Querying structured logs requires you to have defined a struct with the expected
datatypes and to have implemented Detokenize
for it. This boilerplate code
is generated for you via the abigen
and Abigen
builder utilities.
use ethers_core::{abi::Abi, types::Address};
use ethers_contract::{Contract, EthEvent};
use ethers_providers::{Provider, Http, Middleware};
use ethers_signers::Wallet;
use std::convert::TryFrom;
use ethers_core::abi::{Detokenize, Token, InvalidOutputType};
#[derive(Clone, Debug, EthEvent)]
struct ValueChanged {
old_author: Address,
new_author: Address,
old_value: String,
new_value: String,
}
let logs: Vec<ValueChanged> = contract
.event()
.from_block(0u64)
.query()
.await?;
println!("{:?}", logs);
Disclaimer: these above docs have been adapted from the corresponding ethers.js page
Implementations
Creates a new contract from the provided client, abi and address
Returns an Event
builder for the provided event.
Returns an Event
builder with the provided filter.
pub fn event_for_name<D>(&self, name: &str) -> Result<Event<'_, M, D>, Error> where
D: EthLogDecode,
pub fn event_for_name<D>(&self, name: &str) -> Result<Event<'_, M, D>, Error> where
D: EthLogDecode,
Returns an Event
builder with the provided name.
pub fn method<T, D>(
&self,
name: &str,
args: T
) -> Result<ContractCall<M, D>, AbiError> where
T: Tokenize,
D: Detokenize,
pub fn method<T, D>(
&self,
name: &str,
args: T
) -> Result<ContractCall<M, D>, AbiError> where
T: Tokenize,
D: Detokenize,
Returns a transaction builder for the provided function name. If there are
multiple functions with the same name due to overloading, consider using
the method_hash
method instead, since this will use the first match.
pub fn method_hash<T, D>(
&self,
signature: [u8; 4],
args: T
) -> Result<ContractCall<M, D>, AbiError> where
T: Tokenize,
D: Detokenize,
pub fn method_hash<T, D>(
&self,
signature: [u8; 4],
args: T
) -> Result<ContractCall<M, D>, AbiError> where
T: Tokenize,
D: Detokenize,
Returns a transaction builder for the selected function signature. This should be preferred if there are overloaded functions in your smart contract
Returns a new contract instance at address
.
Clones self
internally
Returns a new contract instance using the provided client
Clones self
internally
Methods from Deref<Target = BaseContract>
Returns the ABI encoded data for the provided function and arguments
If the function exists multiple times and you want to use one of the overloaded
versions, consider using encode_with_selector
Returns the ABI encoded data for the provided function selector and arguments
Decodes the provided ABI encoded function arguments with the selected function name.
If the function exists multiple times and you want to use one of the overloaded
versions, consider using decode_with_selector
pub fn decode_event<D>(
&self,
name: &str,
topics: Vec<H256, Global>,
data: Bytes
) -> Result<D, AbiError> where
D: Detokenize,
pub fn decode_event<D>(
&self,
name: &str,
topics: Vec<H256, Global>,
data: Bytes
) -> Result<D, AbiError> where
D: Detokenize,
Decodes for a given event name, given the log.topics
and
log.data
fields from the transaction receipt
Decodes the provided ABI encoded bytes with the selected function selector
Trait Implementations
Auto Trait Implementations
impl<M> RefUnwindSafe for Contract<M> where
M: RefUnwindSafe,
impl<M> UnwindSafe for Contract<M> where
M: RefUnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more
Instruments this type with the provided Span
, returning an
Instrumented
wrapper. Read more
pub fn vzip(self) -> V
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more