Trait NonFungibleTokenApproval

pub trait NonFungibleTokenApproval {
    // Required methods
    fn nft_approve(
        &mut self,
        token_id: TokenId,
        account_id: AccountId,
        msg: Option<String>,
    ) -> Option<Promise>;
    fn nft_revoke(&mut self, token_id: TokenId, account_id: AccountId);
    fn nft_revoke_all(&mut self, token_id: TokenId);
    fn nft_is_approved(
        &self,
        token_id: TokenId,
        approved_account_id: AccountId,
        approval_id: Option<u64>,
    ) -> bool;
}

Trait used when it’s desired to have a non-fungible token that has a traditional escrow or approval system. This allows Alice to allow Bob to take only the token with the unique identifier “19” but not others. It should be noted that in the core non-fungible token standard there is a method to do “transfer and call” which may be preferred over using an approval management standard in certain use cases.

Examples

use std::collections::HashMap;
use near_sdk::{PanicOnDefault, AccountId, PromiseOrValue, near, Promise};
use near_contract_standards::non_fungible_token::{TokenId, NonFungibleToken, NonFungibleTokenApproval};

#[near(contract_state)]
#[derive(PanicOnDefault)]
pub struct Contract {
   tokens: NonFungibleToken,
}

#[near]
impl NonFungibleTokenApproval for Contract {
    #[payable]
    fn nft_approve(&mut self, token_id: TokenId, account_id: AccountId, msg: Option<String>) -> Option<Promise> {
        self.tokens.nft_approve(token_id, account_id, msg)
    }

    #[payable]
    fn nft_revoke(&mut self, token_id: TokenId, account_id: AccountId) {
        self.tokens.nft_revoke(token_id, account_id);
    }

    #[payable]
    fn nft_revoke_all(&mut self, token_id: TokenId) {
        self.tokens.nft_revoke_all(token_id);

    }

    fn nft_is_approved(&self, token_id: TokenId, approved_account_id: AccountId, approval_id: Option<u64>) -> bool {
        self.tokens.nft_is_approved(token_id, approved_account_id, approval_id)
    }
}

Required Methods

fn nft_approve( &mut self, token_id: TokenId, account_id: AccountId, msg: Option<String>, ) -> Option<Promise>

Add an approved account for a specific token.

Requirements

• Caller of the method must attach a deposit of at least 1 yoctoⓃ for security purposes
• Contract MAY require caller to attach larger deposit, to cover cost of storing approver data
• Contract MUST panic if called by someone other than token owner
• Contract MUST panic if addition would cause nft_revoke_all to exceed single-block gas limit
• Contract MUST increment approval ID even if re-approving an account
• If successfully approved or if had already been approved, and if msg is present, contract MUST call nft_on_approve on account_id. See nft_on_approve description below for details.

Arguments:

• token_id: the token for which to add an approval
• account_id: the account to add to approvals
• msg: optional string to be passed to nft_on_approve

Returns void, if no msg given. Otherwise, returns promise call to nft_on_approve, which can resolve with whatever it wants.

fn nft_revoke(&mut self, token_id: TokenId, account_id: AccountId)

Revoke an approved account for a specific token.

Requirements

• Caller of the method must attach a deposit of 1 yoctoⓃ for security purposes
• If contract requires >1yN deposit on nft_approve, contract MUST refund associated storage deposit when owner revokes approval
• Contract MUST panic if called by someone other than token owner

Arguments:

• token_id: the token for which to revoke an approval
• account_id: the account to remove from approvals

fn nft_revoke_all(&mut self, token_id: TokenId)

Revoke all approved accounts for a specific token.

Requirements

• Caller of the method must attach a deposit of 1 yoctoⓃ for security purposes
• If contract requires >1yN deposit on nft_approve, contract MUST refund all associated storage deposit when owner revokes approvals
• Contract MUST panic if called by someone other than token owner

Arguments:

• token_id: the token with approvals to revoke

fn nft_is_approved( &self, token_id: TokenId, approved_account_id: AccountId, approval_id: Option<u64>, ) -> bool

Check if a token is approved for transfer by a given account, optionally checking an approval_id

Arguments:

• token_id: the token for which to revoke an approval
• approved_account_id: the account to check the existence of in approvals
• approval_id: an optional approval ID to check against current approval ID for given account

Returns: if approval_id given, true if approved_account_id is approved with given approval_id otherwise, true if approved_account_id is in list of approved accounts

Implementors

impl NonFungibleTokenApproval for NonFungibleToken