可配置常量
在 Sway 中，您可以定义 configurable 常量，这些常量可以在 SDK 中的合约部署过程中进行更改。以下是定义常量的示例。
contract;
#[allow(dead_code)]
enum EnumWithGeneric<D> {
VariantOne: D,
VariantTwo: (),
}
struct StructWithGeneric<D> {
field_1: D,
field_2: u64,
}
configurable {
BOOL: bool = true,
U8: u8 = 8,
U16: u16 = 16,
U32: u32 = 32,
U64: u64 = 63,
U256: u256 = 0x0000000000000000000000000000000000000000000000000000000000000008u256,
B256: b256 = 0x0101010101010101010101010101010101010101010101010101010101010101,
STR_4: str[4] = __to_str_array("fuel"),
TUPLE: (u8, bool) = (8, true),
ARRAY: [u32; 3] = [253, 254, 255],
STRUCT: StructWithGeneric<u8> = StructWithGeneric {
field_1: 8,
field_2: 16,
},
ENUM: EnumWithGeneric<bool> = EnumWithGeneric::VariantOne(true),
}
//U128: u128 = 128, //TODO: add once https://github.com/FuelLabs/sway/issues/5356 is done
abi TestContract {
fn return_configurables() -> (bool, u8, u16, u32, u64, u256, b256, str[4], (u8, bool), [u32; 3], StructWithGeneric<u8>, EnumWithGeneric<bool>);
}
impl TestContract for Contract {
fn return_configurables() -> (bool, u8, u16, u32, u64, u256, b256, str[4], (u8, bool), [u32; 3], StructWithGeneric<u8>, EnumWithGeneric<bool>) {
(BOOL, U8, U16, U32, U64, U256, B256, STR_4, TUPLE, ARRAY, STRUCT, ENUM)
}
}
每个可配置的常量将在 SDK 中获得一个专用的 with 方法。例如，常量 STR_4 将获得 with_STR_4 方法，该方法接受与合约代码中定义的相同类型。以下是一个示例，其中我们链接了几个 with 方法，并使用新常量部署了合约。
abigen!(Contract(
name = "MyContract",
abi = "e2e/sway/contracts/configurables/out/release/configurables-abi.json"
));
let wallet = launch_provider_and_get_wallet().await?;
let str_4: SizedAsciiString<4> = "FUEL".try_into()?;
let new_struct = StructWithGeneric {
field_1: 16u8,
field_2: 32,
};
let new_enum = EnumWithGeneric::VariantTwo;
let configurables = MyContractConfigurables::default()
.with_BOOL(false)?
.with_U8(7)?
.with_U16(15)?
.with_U32(31)?
.with_U64(63)?
.with_U256(U256::from(8))?
.with_B256(Bits256([2; 32]))?
.with_STR_4(str_4.clone())?
.with_TUPLE((7, false))?
.with_ARRAY([252, 253, 254])?
.with_STRUCT(new_struct.clone())?
.with_ENUM(new_enum.clone())?;
let contract_id = Contract::load_from(
"sway/contracts/configurables/out/release/configurables.bin",
LoadConfiguration::default().with_configurables(configurables),
)?
.deploy(&wallet, TxPolicies::default())
.await?;
let contract_instance = MyContract::new(contract_id, wallet.clone());