write-contracts

Write Contracts Skill

Core Rules

Digital Assets (NFTs) ⭐ CRITICAL

1. ALWAYS use Digital Asset (DA) standard for ALL NFT-related contracts (collections, marketplaces, minting)
2. ALWAYS import aptos_token_objects::collection and aptos_token_objects::token modules
3. ALWAYS use Object<AptosToken> for NFT references (NOT generic Object<T>)
4. NEVER use legacy TokenV1 standard or aptos_token::token module (deprecated)
5. See ../../../patterns/move/DIGITAL_ASSETS.md for complete NFT patterns

Object Model

1. ALWAYS use Object<T> for all object references (NEVER raw addresses)
2. Generate all refs (TransferRef, DeleteRef) in constructor before ConstructorRef destroyed
3. Return Object<T> from constructors (NEVER return ConstructorRef)
4. Verify ownership with object::owner(obj) == signer::address_of(user)
5. Use object::generate_signer(&constructor_ref) for object signers
6. Use named objects for singletons: object::create_named_object(creator, seed)

Security

1. ALWAYS verify signer authority in entry functions: assert!(signer::address_of(user) == expected, E_UNAUTHORIZED)
2. ALWAYS validate inputs: non-zero amounts, address validation, string length checks
3. NEVER expose &mut references in public functions
4. NEVER skip signer verification in entry functions

Modern Syntax

1. Use inline functions and lambdas for iteration
2. Use receiver-style method calls: obj.is_owner(user) (define first param as self)
3. Use vector indexing: vector[index] instead of vector::borrow()
4. Use direct named addresses: @marketplace_addr (NOT helper functions)

Required Patterns

1. Use init_module for contract initialization on deployment
2. Emit events for ALL significant activities (create, transfer, update, delete)
3. Define clear error constants with descriptive names (E_NOT_OWNER, E_INSUFFICIENT_BALANCE)

Testability