Trait scrypto_test::prelude::AsMut
1.0.0 · source · pub trait AsMut<T>where
T: ?Sized,{
// Required method
fn as_mut(&mut self) -> &mut T;
}Expand description
Used to do a cheap mutable-to-mutable reference conversion.
This trait is similar to AsRef but used for converting between mutable
references. If you need to do a costly conversion it is better to
implement From with type &mut T or write a custom function.
Note: This trait must not fail. If the conversion can fail, use a
dedicated method which returns an Option<T> or a Result<T, E>.
§Generic Implementations
AsMut auto-dereferences if the inner type is a mutable reference
(e.g.: foo.as_mut() will work the same if foo has type &mut Foo or &mut &mut Foo).
Note that due to historic reasons, the above currently does not hold generally for all
mutably dereferenceable types, e.g. foo.as_mut() will not work the same as
Box::new(foo).as_mut(). Instead, many smart pointers provide an as_mut implementation which
simply returns a reference to the pointed-to value (but do not perform a cheap
reference-to-reference conversion for that value). However, AsMut::as_mut should not be
used for the sole purpose of mutable dereferencing; instead ‘Deref coercion’ can be used:
let mut x = Box::new(5i32);
// Avoid this:
// let y: &mut i32 = x.as_mut();
// Better just write:
let y: &mut i32 = &mut x;Types which implement DerefMut should consider to add an implementation of AsMut<T> as
follows:
impl<T> AsMut<T> for SomeType
where
<SomeType as Deref>::Target: AsMut<T>,
{
fn as_mut(&mut self) -> &mut T {
self.deref_mut().as_mut()
}
}§Reflexivity
Ideally, AsMut would be reflexive, i.e. there would be an impl<T: ?Sized> AsMut<T> for T
with as_mut simply returning its argument unchanged.
Such a blanket implementation is currently not provided due to technical restrictions of
Rust’s type system (it would be overlapping with another existing blanket implementation for
&mut T where T: AsMut<U> which allows AsMut to auto-dereference, see “Generic
Implementations” above).
A trivial implementation of AsMut<T> for T must be added explicitly for a particular type T
where needed or desired. Note, however, that not all types from std contain such an
implementation, and those cannot be added by external code due to orphan rules.
§Examples
Using AsMut as trait bound for a generic function, we can accept all mutable references that
can be converted to type &mut T. Unlike dereference, which has a single target type,
there can be multiple implementations of AsMut for a type. In particular, Vec<T> implements
both AsMut<Vec<T>> and AsMut<[T]>.
In the following, the example functions caesar and null_terminate provide a generic
interface which work with any type that can be converted by cheap mutable-to-mutable conversion
into a byte slice ([u8]) or byte vector (Vec<u8>), respectively.
struct Document {
info: String,
content: Vec<u8>,
}
impl<T: ?Sized> AsMut<T> for Document
where
Vec<u8>: AsMut<T>,
{
fn as_mut(&mut self) -> &mut T {
self.content.as_mut()
}
}
fn caesar<T: AsMut<[u8]>>(data: &mut T, key: u8) {
for byte in data.as_mut() {
*byte = byte.wrapping_add(key);
}
}
fn null_terminate<T: AsMut<Vec<u8>>>(data: &mut T) {
// Using a non-generic inner function, which contains most of the
// functionality, helps to minimize monomorphization overhead.
fn doit(data: &mut Vec<u8>) {
let len = data.len();
if len == 0 || data[len-1] != 0 {
data.push(0);
}
}
doit(data.as_mut());
}
fn main() {
let mut v: Vec<u8> = vec![1, 2, 3];
caesar(&mut v, 5);
assert_eq!(v, [6, 7, 8]);
null_terminate(&mut v);
assert_eq!(v, [6, 7, 8, 0]);
let mut doc = Document {
info: String::from("Example"),
content: vec![17, 19, 8],
};
caesar(&mut doc, 1);
assert_eq!(doc.content, [18, 20, 9]);
null_terminate(&mut doc);
assert_eq!(doc.content, [18, 20, 9, 0]);
}Note, however, that APIs don’t need to be generic. In many cases taking a &mut [u8] or
&mut Vec<u8>, for example, is the better choice (callers need to pass the correct type then).
Required Methods§
Implementors§
impl AsMut<VersionedAccountAuthorizedDepositor> for AccountAuthorizedDepositorEntryPayload
impl AsMut<VersionedAccountDepositRule> for AccountDepositRuleFieldPayload
impl AsMut<VersionedAccountResourcePreference> for AccountResourcePreferenceEntryPayload
impl AsMut<VersionedAccountResourceVault> for AccountResourceVaultEntryPayload
impl AsMut<VersionedMetadataEntry> for MetadataEntryEntryPayload
impl AsMut<VersionedRoleAssignmentAccessRule> for RoleAssignmentAccessRuleEntryPayload
impl AsMut<VersionedRoleAssignmentOwner> for RoleAssignmentOwnerFieldPayload
impl AsMut<VersionedComponentRoyaltyAccumulator> for ComponentRoyaltyAccumulatorFieldPayload
impl AsMut<VersionedComponentRoyaltyMethodAmount> for ComponentRoyaltyMethodAmountEntryPayload
impl AsMut<ResourceOrNonFungible> for AccountAuthorizedDepositorKeyPayload
impl AsMut<VersionedAccessControllerState> for AccessControllerStateFieldPayload
impl AsMut<VersionedConsensusManagerConfiguration> for ConsensusManagerConfigurationFieldPayload
impl AsMut<VersionedConsensusManagerCurrentProposalStatistic> for ConsensusManagerCurrentProposalStatisticFieldPayload
impl AsMut<VersionedConsensusManagerCurrentValidatorSet> for ConsensusManagerCurrentValidatorSetFieldPayload
impl AsMut<VersionedConsensusManagerProposerMilliTimestamp> for ConsensusManagerProposerMilliTimestampFieldPayload
impl AsMut<VersionedConsensusManagerProposerMinuteTimestamp> for ConsensusManagerProposerMinuteTimestampFieldPayload
impl AsMut<VersionedConsensusManagerRegisteredValidatorByStake> for ConsensusManagerRegisteredValidatorByStakeEntryPayload
impl AsMut<VersionedConsensusManagerState> for ConsensusManagerStateFieldPayload
impl AsMut<VersionedConsensusManagerValidatorRewards> for ConsensusManagerValidatorRewardsFieldPayload
impl AsMut<VersionedFungibleResourceManagerDivisibility> for FungibleResourceManagerDivisibilityFieldPayload
impl AsMut<VersionedFungibleResourceManagerTotalSupply> for FungibleResourceManagerTotalSupplyFieldPayload
impl AsMut<VersionedFungibleVaultBalance> for FungibleVaultBalanceFieldPayload
impl AsMut<VersionedFungibleVaultFreezeStatus> for FungibleVaultFreezeStatusFieldPayload
impl AsMut<VersionedFungibleVaultLockedBalance> for FungibleVaultLockedBalanceFieldPayload
impl AsMut<VersionedNonFungibleResourceManagerIdType> for NonFungibleResourceManagerIdTypeFieldPayload
impl AsMut<VersionedNonFungibleResourceManagerMutableFields> for NonFungibleResourceManagerMutableFieldsFieldPayload
impl AsMut<VersionedNonFungibleResourceManagerTotalSupply> for NonFungibleResourceManagerTotalSupplyFieldPayload
impl AsMut<VersionedNonFungibleVaultBalance> for NonFungibleVaultBalanceFieldPayload
impl AsMut<VersionedNonFungibleVaultFreezeStatus> for NonFungibleVaultFreezeStatusFieldPayload
impl AsMut<VersionedNonFungibleVaultLockedResource> for NonFungibleVaultLockedResourceFieldPayload
impl AsMut<VersionedNonFungibleVaultNonFungible> for NonFungibleVaultNonFungibleEntryPayload
impl AsMut<VersionedPackageBlueprintVersionAuthConfig> for PackageBlueprintVersionAuthConfigEntryPayload
impl AsMut<VersionedPackageBlueprintVersionDefinition> for PackageBlueprintVersionDefinitionEntryPayload
impl AsMut<VersionedPackageBlueprintVersionDependencies> for PackageBlueprintVersionDependenciesEntryPayload
impl AsMut<VersionedPackageBlueprintVersionRoyaltyConfig> for PackageBlueprintVersionRoyaltyConfigEntryPayload
impl AsMut<VersionedPackageCodeInstrumentedCode> for PackageCodeInstrumentedCodeEntryPayload
impl AsMut<VersionedPackageCodeOriginalCode> for PackageCodeOriginalCodeEntryPayload
impl AsMut<VersionedPackageCodeVmType> for PackageCodeVmTypeEntryPayload
impl AsMut<VersionedPackageRoyaltyAccumulator> for PackageRoyaltyAccumulatorFieldPayload
impl AsMut<VersionedValidatorProtocolUpdateReadinessSignal> for ValidatorProtocolUpdateReadinessSignalFieldPayload
impl AsMut<VersionedValidatorState> for ValidatorStateFieldPayload
impl AsMut<NonFungibleLocalId> for NonFungibleResourceManagerDataKeyPayload
impl AsMut<NonFungibleLocalId> for NonFungibleVaultNonFungibleKeyPayload
impl AsMut<VersionedSchema<ScryptoCustomSchema>> for PackageSchemaEntryPayload
impl AsMut<VersionedMultiResourcePoolState> for MultiResourcePoolStateFieldPayload
impl AsMut<VersionedOneResourcePoolState> for OneResourcePoolStateFieldPayload
impl AsMut<VersionedTwoResourcePoolState> for TwoResourcePoolStateFieldPayload
impl AsMut<str> for str
impl AsMut<str> for String
impl AsMut<str> for AliasableString
impl AsMut<String> for MetadataEntryKeyPayload
impl AsMut<String> for ComponentRoyaltyMethodAmountKeyPayload
impl AsMut<ComponentAddress> for ConsensusManagerRegisteredValidatorByStakeKeyPayload
impl AsMut<ResourceAddress> for AccountResourcePreferenceKeyPayload
impl AsMut<ResourceAddress> for AccountResourceVaultKeyPayload
impl AsMut<SchemaHash> for PackageSchemaKeyPayload
impl AsMut<BlueprintVersionKey> for PackageBlueprintVersionAuthConfigKeyPayload
impl AsMut<BlueprintVersionKey> for PackageBlueprintVersionDefinitionKeyPayload
impl AsMut<BlueprintVersionKey> for PackageBlueprintVersionDependenciesKeyPayload
impl AsMut<BlueprintVersionKey> for PackageBlueprintVersionRoyaltyConfigKeyPayload
impl AsMut<CodeHash> for PackageCodeInstrumentedCodeKeyPayload
impl AsMut<CodeHash> for PackageCodeOriginalCodeKeyPayload
impl AsMut<CodeHash> for PackageCodeVmTypeKeyPayload
impl AsMut<ModuleRoleKey> for RoleAssignmentAccessRuleKeyPayload
impl<A> AsMut<[<A as Array>::Item]> for SmallVec<A>where
A: Array,
impl<Data> AsMut<Data> for NonFungibleResourceManagerDataEntryPayload<Data>where
Data: NonFungibleResourceManagerDataContentMarker,
impl<L, R> AsMut<str> for Either<L, R>
impl<L, R> AsMut<CStr> for Either<L, R>
Requires crate feature use_std.
impl<L, R> AsMut<OsStr> for Either<L, R>
Requires crate feature use_std.
impl<L, R> AsMut<Path> for Either<L, R>
Requires crate feature use_std.