Struct TokenAttributesMapper 

pub struct TokenAttributesMapper<SA, A = CurrentStorage>
where
    SA: StorageMapperApi,
{ /* private fields */ }

Specialized mapper for managing NFT/SFT token attributes with efficient storage and bidirectional lookup capabilities. Maps token attributes to nonces and vice versa, enabling efficient queries by both token nonce and attribute values.

Storage Layout

The mapper uses a sophisticated multi-key storage layout for efficient lookups:

base_key + ".counter" → u8                    // Global token ID counter
base_key + ".mapping" + token_id → u8         // Token ID to internal mapping ID
base_key + ".attr" + mapping + nonce → T     // Token attributes by nonce
base_key + ".nonce" + mapping + attr → u64   // Nonce lookup by attributes

Main Operations

Attribute Management

• Set: Store attributes for token nonce with set()
• Update: Modify existing attributes with update()
• Clear: Remove attributes with clear()
• Get: Retrieve attributes by nonce with get_attributes()

Bidirectional Lookup

• Nonce by Attributes: Find nonce for specific attributes with get_nonce()
• Attributes by Nonce: Find attributes for specific nonce with get_attributes()
• Existence Checks: Verify presence with has_attributes(), has_nonce()

Internal Mapping

• Space Optimization: Uses u8 internal IDs to reduce storage keys
• Counter Management: Automatically assigns mapping IDs up to 255 tokens
• Collision Avoidance: Each token ID gets unique mapping space

Trade-offs

Advantages:

• Bidirectional lookup (nonce ↔ attributes) in O(1) time
• Space-efficient storage with internal mapping compression
• Prevents duplicate attribute sets per token
• Supports any encodable attribute type

Limitations:

• Maximum 255 different token IDs per mapper instance
• Attributes cannot be changed once set (use update carefully)
• Complex storage layout increases implementation overhead
• No iteration capabilities over stored mappings

Implementations

impl<SA> TokenAttributesMapper<SA, CurrentStorage>

where SA: StorageMapperApi,

pub fn set<T: TopEncode + TopDecode + NestedEncode + NestedDecode, M: ManagedTypeApi>( &self, token_id: &EsdtTokenIdentifier<M>, token_nonce: u64, attributes: &T, )

pub fn update<T: TopEncode + TopDecode + NestedEncode + NestedDecode, M: ManagedTypeApi>( &self, token_id: &EsdtTokenIdentifier<M>, token_nonce: u64, attributes: &T, )

Use carefully. Update should be used mainly when backed up by the protocol.

pub fn clear<T: TopEncode + TopDecode + NestedEncode + NestedDecode, M: ManagedTypeApi>( &self, token_id: &EsdtTokenIdentifier<M>, token_nonce: u64, )

impl<SA, A> TokenAttributesMapper<SA, A>

where SA: StorageMapperApi, A: StorageAddress<SA>,

pub fn has_attributes<M: ManagedTypeApi>( &self, token_id: &EsdtTokenIdentifier<M>, token_nonce: u64, ) -> bool

pub fn has_nonce<T: TopEncode + TopDecode + NestedEncode + NestedDecode, M: ManagedTypeApi>( &self, token_id: &EsdtTokenIdentifier<M>, attr: &T, ) -> bool

pub fn get_attributes<T: TopEncode + TopDecode + NestedEncode + NestedDecode, M: ManagedTypeApi>( &self, token_id: &EsdtTokenIdentifier<M>, token_nonce: u64, ) -> T

pub fn get_nonce<T: TopEncode + TopDecode + NestedEncode + NestedDecode, M: ManagedTypeApi>( &self, token_id: &EsdtTokenIdentifier<M>, attr: &T, ) -> u64

Trait Implementations

impl<SA> StorageMapper<SA> for TokenAttributesMapper<SA, CurrentStorage>

where SA: StorageMapperApi,

fn new(base_key: StorageKey<SA>) -> Self

Will be called automatically by the #[storage_mapper] annotation generated code.

impl<SA> StorageMapperFromAddress<SA> for TokenAttributesMapper<SA, ManagedAddress<SA>>

where SA: StorageMapperApi,

fn new_from_address( address: ManagedAddress<SA>, base_key: StorageKey<SA>, ) -> Self

Will be called automatically by the #[storage_mapper_from_address] annotation generated code.