Trait scrypto_test::prelude::rust::prelude::AsRef

1.0.0 · source ·

pub trait AsRef<T>where
    T: ?Sized,{
    // Required method
    fn as_ref(&self) -> &T;
}

Expand description

Used to do a cheap reference-to-reference conversion.

This trait is similar to AsMut which is used for converting between mutable references. If you need to do a costly conversion it is better to implement From with type &T or write a custom function.

§Relation to `Borrow`

AsRef has the same signature as Borrow, but Borrow is different in a few aspects:

Unlike AsRef, Borrow has a blanket impl for any T, and can be used to accept either a reference or a value. (See also note on AsRef’s reflexibility below.)
Borrow also requires that Hash, Eq and Ord for a borrowed value are equivalent to those of the owned value. For this reason, if you want to borrow only a single field of a struct you can implement AsRef, but not Borrow.

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

AsRef auto-dereferences if the inner type is a reference or a mutable reference (e.g.: foo.as_ref() will work the same if foo has type &mut Foo or &&mut Foo).

Note that due to historic reasons, the above currently does not hold generally for all dereferenceable types, e.g. foo.as_ref() will not work the same as Box::new(foo).as_ref(). Instead, many smart pointers provide an as_ref 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, AsRef::as_ref should not be used for the sole purpose of dereferencing; instead ‘Deref coercion’ can be used:

let x = Box::new(5i32);
// Avoid this:
// let y: &i32 = x.as_ref();
// Better just write:
let y: &i32 = &x;

Types which implement Deref should consider implementing AsRef<T> as follows:

impl<T> AsRef<T> for SomeType
where
    T: ?Sized,
    <SomeType as Deref>::Target: AsRef<T>,
{
    fn as_ref(&self) -> &T {
        self.deref().as_ref()
    }
}

§Reflexivity

Ideally, AsRef would be reflexive, i.e. there would be an impl<T: ?Sized> AsRef<T> for T with as_ref 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 &T where T: AsRef which allows AsRef to auto-dereference, see “Generic Implementations” above).

A trivial implementation of AsRef<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

By using trait bounds we can accept arguments of different types as long as they can be converted to the specified type T.

For example: By creating a generic function that takes an AsRef<str> we express that we want to accept all references that can be converted to &str as an argument. Since both String and &str implement AsRef<str> we can accept both as input argument.

fn is_hello<T: AsRef<str>>(s: T) {
   assert_eq!("hello", s.as_ref());
}

let s = "hello";
is_hello(s);

let s = "hello".to_string();
is_hello(s);

Required Methods§

source

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

Trait scrypto_test::prelude::rust::prelude::AsRef

§Relation to Borrow

§Generic Implementations

§Reflexivity

§Examples

Required Methods§

fn as_ref(&self) -> &T

Implementors§

impl AsRef<VersionedAccountAuthorizedDepositor> for AccountAuthorizedDepositorEntryPayload

impl AsRef<VersionedAccountDepositRule> for AccountDepositRuleFieldPayload

impl AsRef<VersionedAccountResourcePreference> for AccountResourcePreferenceEntryPayload

impl AsRef<VersionedAccountResourceVault> for AccountResourceVaultEntryPayload

impl AsRef<VersionedMetadataEntry> for MetadataEntryEntryPayload

impl AsRef<VersionedRoleAssignmentAccessRule> for RoleAssignmentAccessRuleEntryPayload

impl AsRef<VersionedRoleAssignmentOwner> for RoleAssignmentOwnerFieldPayload

impl AsRef<VersionedComponentRoyaltyAccumulator> for ComponentRoyaltyAccumulatorFieldPayload

impl AsRef<VersionedComponentRoyaltyMethodAmount> for ComponentRoyaltyMethodAmountEntryPayload

impl AsRef<ResourceOrNonFungible> for AccountAuthorizedDepositorKeyPayload

impl AsRef<VersionedAccessControllerState> for AccessControllerStateFieldPayload

impl AsRef<VersionedConsensusManagerConfiguration> for ConsensusManagerConfigurationFieldPayload

impl AsRef<VersionedConsensusManagerCurrentProposalStatistic> for ConsensusManagerCurrentProposalStatisticFieldPayload

impl AsRef<VersionedConsensusManagerCurrentValidatorSet> for ConsensusManagerCurrentValidatorSetFieldPayload

impl AsRef<VersionedConsensusManagerProposerMilliTimestamp> for ConsensusManagerProposerMilliTimestampFieldPayload

impl AsRef<VersionedConsensusManagerProposerMinuteTimestamp> for ConsensusManagerProposerMinuteTimestampFieldPayload

impl AsRef<VersionedConsensusManagerRegisteredValidatorByStake> for ConsensusManagerRegisteredValidatorByStakeEntryPayload

impl AsRef<VersionedConsensusManagerState> for ConsensusManagerStateFieldPayload

impl AsRef<VersionedConsensusManagerValidatorRewards> for ConsensusManagerValidatorRewardsFieldPayload

impl AsRef<VersionedFungibleResourceManagerDivisibility> for FungibleResourceManagerDivisibilityFieldPayload

impl AsRef<VersionedFungibleResourceManagerTotalSupply> for FungibleResourceManagerTotalSupplyFieldPayload

impl AsRef<VersionedFungibleVaultBalance> for FungibleVaultBalanceFieldPayload

impl AsRef<VersionedFungibleVaultFreezeStatus> for FungibleVaultFreezeStatusFieldPayload

impl AsRef<VersionedFungibleVaultLockedBalance> for FungibleVaultLockedBalanceFieldPayload

impl AsRef<VersionedNonFungibleResourceManagerIdType> for NonFungibleResourceManagerIdTypeFieldPayload

impl AsRef<VersionedNonFungibleResourceManagerMutableFields> for NonFungibleResourceManagerMutableFieldsFieldPayload

impl AsRef<VersionedNonFungibleResourceManagerTotalSupply> for NonFungibleResourceManagerTotalSupplyFieldPayload

impl AsRef<VersionedNonFungibleVaultBalance> for NonFungibleVaultBalanceFieldPayload

impl AsRef<VersionedNonFungibleVaultFreezeStatus> for NonFungibleVaultFreezeStatusFieldPayload

impl AsRef<VersionedNonFungibleVaultLockedResource> for NonFungibleVaultLockedResourceFieldPayload

impl AsRef<VersionedNonFungibleVaultNonFungible> for NonFungibleVaultNonFungibleEntryPayload

impl AsRef<VersionedPackageBlueprintVersionAuthConfig> for PackageBlueprintVersionAuthConfigEntryPayload

impl AsRef<VersionedPackageBlueprintVersionDefinition> for PackageBlueprintVersionDefinitionEntryPayload

impl AsRef<VersionedPackageBlueprintVersionDependencies> for PackageBlueprintVersionDependenciesEntryPayload

impl AsRef<VersionedPackageBlueprintVersionRoyaltyConfig> for PackageBlueprintVersionRoyaltyConfigEntryPayload

impl AsRef<VersionedPackageCodeInstrumentedCode> for PackageCodeInstrumentedCodeEntryPayload

impl AsRef<VersionedPackageCodeOriginalCode> for PackageCodeOriginalCodeEntryPayload

impl AsRef<VersionedPackageCodeVmType> for PackageCodeVmTypeEntryPayload

impl AsRef<VersionedPackageRoyaltyAccumulator> for PackageRoyaltyAccumulatorFieldPayload

impl AsRef<VersionedValidatorProtocolUpdateReadinessSignal> for ValidatorProtocolUpdateReadinessSignalFieldPayload

impl AsRef<VersionedValidatorState> for ValidatorStateFieldPayload

impl AsRef<NonFungibleLocalId> for NonFungibleResourceManagerDataKeyPayload

impl AsRef<NonFungibleLocalId> for NonFungibleVaultNonFungibleKeyPayload

impl AsRef<VersionedSchema<ScryptoCustomSchema>> for PackageSchemaEntryPayload

impl AsRef<VersionedMultiResourcePoolState> for MultiResourcePoolStateFieldPayload

impl AsRef<VersionedOneResourcePoolState> for OneResourcePoolStateFieldPayload

impl AsRef<VersionedTwoResourcePoolState> for TwoResourcePoolStateFieldPayload

impl AsRef<str> for str

impl AsRef<str> for String

impl AsRef<str> for AliasableString

impl AsRef<u8> for u5

impl AsRef<String> for MetadataEntryKeyPayload

impl AsRef<String> for ComponentRoyaltyMethodAmountKeyPayload

impl AsRef<ComponentAddress> for ConsensusManagerRegisteredValidatorByStakeKeyPayload

impl AsRef<Hash> for Hash

impl AsRef<Hash> for SchemaHash

impl AsRef<Hash> for CodeHash

impl AsRef<Hash> for FlashTransactionHash

impl AsRef<Hash> for IntentHash

impl AsRef<Hash> for NotarizedTransactionHash

impl AsRef<Hash> for SignedIntentHash

impl AsRef<Hash> for SystemTransactionHash

impl AsRef<ResourceAddress> for AccountResourcePreferenceKeyPayload

impl AsRef<ResourceAddress> for AccountResourceVaultKeyPayload

impl AsRef<SchemaHash> for PackageSchemaKeyPayload

impl AsRef<BlueprintVersionKey> for PackageBlueprintVersionAuthConfigKeyPayload

impl AsRef<BlueprintVersionKey> for PackageBlueprintVersionDefinitionKeyPayload

impl AsRef<BlueprintVersionKey> for PackageBlueprintVersionDependenciesKeyPayload

impl AsRef<BlueprintVersionKey> for PackageBlueprintVersionRoyaltyConfigKeyPayload

impl AsRef<CodeHash> for PackageCodeInstrumentedCodeKeyPayload

impl AsRef<CodeHash> for PackageCodeOriginalCodeKeyPayload

impl AsRef<CodeHash> for PackageCodeVmTypeKeyPayload

§Relation to `Borrow`