Questions tagged [erc-721]

Relating to ERC-721, the standard for Non-Fungible Tokens (also known as Deeds)

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ERC721 Transfer Event issue

Looking at the open-zeppelin ERC721 Contract's code, I see that the very last thing that its mint function is doing is call emit on the contract's pre-defined Transfer event. My question is: how do ...
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ERC721 Contract vs. Auction Contract - Architectural Approach [duplicate]

I'm working on a new ERC721 Crypto-Collectible project, which also means creating an Auction and Marketplace functionalities into the whole thing. Should I just start with a basic ERC721 Contract - ...
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Setting Fees/Prices for Items

I have a question on setting prices for the cards in the card game I'm working on. Right now, I have 2 cards available but there will be more (maybe a couple dozen). I store each card as a struct ...
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Getting ERC721 Metadata Into My Webpage

This likely goes beyond Solidity code so may be off topic, apologies in advance if that's the case. Working on a collectible card game based on ERC721 with the metadata extension. When a person "...
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Pay for the users gas fee (ERC-721)

Is there a way for an NFT (ERC-721) so the contract creator pays for the gas fee when the user's trade tokens? Or add some sort of middleware CC payment so for the user that is not tech salvage not ...
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ERC721 - How is gas worked out with TokenID?

ERC721 - I have minted a tokenid (tokenid=444) and my account owns it. When I try and transfer it, I get this message stating the gas cost is the normally calculated one and the total cost has the ...
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1answer
130 views

What is the difference between approval and ownership in ERC721?

I saw the contract as getApproved and ownerOf functions. What is the difference between owning the token under ERC721 and having approval? When the tokenid is transferred does that transfer ownership ...
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1answer
404 views

How to import files into remix (ERC721 contract)?

I get this error - Unable to import "undefined": Not Found And this flashes onto the screen - Loading https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/introspection/...
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How would I use Web3.js to fetch a user's ERC721 tokens?

How would I use Web3.js to see which ERC721 tokens a user has in their wallet and what the ID or index for those tokens is?
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3answers
285 views

ERC721 - Create 1000 tokens in one function call

I have implemented a contract where a set of ERC721 tokens should be generated with a function call in private net. Code as follows : function mint( address _owner, uint256[] _id ) ...
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2answers
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How do you add miner address so that it can mint tokens?

I have ERC721 that I'm making. function mint(address to, uint256 tokenId) public onlyMinter returns (bool) { _mint(to, tokenId); return true; } How can I add an address so that it is able ...
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What does the single line “_;” in OpenZeppelin's onlyMinter() function do? [duplicate]

In onlyMinter(), there is a line with only _;. I'm having troubles adding a minter address, so I'm just checking the various contracts that go into ERC721. The function is modifier onlyMinter() { ...
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No events were emitted - Exchanging ERC721 Tokens

Function to exchange ERC721 Tokens between two addresses. I am implementing this on truffle and openzeppelin 2.10. Two different tokens should be exchanged between two addresses. Here's my contract ...
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2answers
289 views

How do I transfer an arbitrary erc 721 asset from a smart contract?

I'm trying to work with ERC 721 tokens in such a way that my contract freezes and unfreezes them (based on some conditions) but I'm having trouble wrapping function calls to the ERC 721 token contract ...
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1answer
78 views

ERC721 Default Implementation

I’m working on a card game. Right now it is really simple. There are orcs and cards. Both should be implemented as ERC 721. What would be the most natural way to make the orc an ERC-721 token? ...
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226 views

How to integrate ERC 721 and 20 to create semi-fungible tokens?

ERC 721 defines non-fungible tokens where each token is unique. But if one needs to create a token where there is a limited supply of various types, is there a an effective way to accomplish this by ...
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1answer
242 views

How to ERC721 token using external contract to msg.sender?

I have Caller and ERC721 contract just like this : contract SampleToken is ERC721MetadataMintable { string private name; string private symbol; constructor (address _creator, string _name,...
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5answers
971 views

ERC721 Error: invalid number value arg=“_tokenId”, coderType=“uint256”, value=

MyERC721: pragma solidity ^0.5.0; import "openzeppelin-solidity/contracts/ownership/Ownable.sol"; import "openzeppelin-solidity/contracts/token/ERC721/ERC721Full.sol"; import "openzeppelin-solidity/...
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Member “transfer” not found or not visible after argument-dependent [duplicate]

I am writing ERC721 contract with truffle. I have recently upgrade solc to 0.5.0 due to openzepplin compiler version. Read about the changes to the 0.5.0 version unfortunately I am unable to resolve ...
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2answers
250 views

How to estimate ERC721 mint transaction?

My contract; contract My721 is ERC721Full, ERC721Mintable, Ownable { constructor() ERC721Full("My721", "MY721") public {} function mintUniqueTokenTo (address _to, uint256 _tokenId, string ...
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143 views

Deploy ERC721 tokens to many addresses

How to I transfer many of my ERC721 tokens to many addresses? MyERC721: function mintUniqueTokenTo ( address _to, uint256 _tokenId, string _tokenURI // Store, receipient'...
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3answers
125 views

Function that returns address if is passed or msg.sender

I'm implementing an ERC721 contract and I want to execute the following logic. This is what I want: If the user pass to a method an address, return that address, if not, return the user's address. I ...
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2answers
470 views

How to check Balance & send ERC721 Tokens

I have SPH ERC721 Tokens. How can I check balance like ERC20 and send ERC721 tokens token to Exchange or in other wallet ?
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1answer
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what is the equivalent of encodeFunctionSignature for web3.js version ^0.20.6

I want to check if a specific contract deployed at an address is an erc721 contract. I found out that most of the erc721 contracts should have safeTransferFrom function implemented. (except ...
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1answer
259 views

ERC721 Metadata Creation (Newbie Question) [closed]

Complete newbie here so thanks in advance for tolerating the ignorance that follows. Working on creating a little card game to learn solidity and have reached the part where I need to assign metadata ...
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1answer
95 views

Distinguishing erc721 transactions from the response of txlist on etherscan

I am making some erc721 transactions. I can retrieve those transactions using the etherscan api like this https://api.etherscan.io/api?module=contract&action=txlist&address=...
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2answers
476 views

Should My ERC721 Show In A Wallet?

We've created and deployed a contract to mint and issue an ERC721 token. I've gone to our admin page in our dapp and "sent" 3 of them to my personal address. When I check my address in etherscan I ...
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2answers
350 views

What is the difference between the transfer and transferFrom function in an ERC721 contract

Using web.js, I am trying to transfer erc721 tokens across different addresses. In case of cryptokitties, I can do the transfer using transfer function only while in case of cryptoheroes, I can use ...
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1answer
121 views

Error: Invalid number of arguments to Solidity function when calling safeTransferFrom function

I want to call the safeTransferFrom function to transfer ERC721 tokens. I am using the following code: var contract = this.web3.eth.contract(JSON.parse(contractabierc721)).at(contractAddress); // ...
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1answer
45 views

Is it possible to check the Thrid party token ( USDT ) within my ERC223 contracts?

I want to check how many tokens are received in my contracts, so that I am able to allocate MY TOKENS to the TOKEN Sender. I tried several ways like approveAndCall, but its not working. I don't ...
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1answer
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ERC 721 card game

The general concept of ERC 721 is clear to me. My question is more about the contract deployment. I want to have 100 unique cards, So I thought of these two implementations: Having an initial supply(...
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2answers
358 views

how to get Token_Id from ERC721 smart contract

How do I retriever Token_Id of cryptokitties from ERC721 Smart contract Smart contract address : https://etherscan.io/address/0x06012c8cf97bead5deae237070f9587f8e7a266d#code
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1answer
562 views

Get ERC721 token total supply using web3.js

I created a simple contract which basically does nothing but mints new ERC721 tokens. The solidity code for it is as follows: struct Monster { string name; uint level; uint ...
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1answer
353 views

List holders and tokens for an ERC-721 contract

Given a contract, I want to map the holders to their token ids. For example, the contract 0xFBeef911Dc5821886e1dda71586d90eD28174B7d is an ERC-721 contract for KnownOriginDigitalAsset. Etherscan ...
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2answers
176 views

Ethereum implementation of a non-fungible but divisible token? (ERC721 seems not to work for that)

I am struggling currently with finding the right implementation possibility for a token with the following properties: Asset-backed token based on a non-fungible asset (like a piece of art) More than ...
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1answer
47 views

Can we create a token with some data inside it?

I wane to write some data (like a link to some file etc) in a token, and once someone sends it from one address to another, that data should be sent as well. Is there anyway we can do now? or you this ...
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603 views

How etherscan.io is able to track ERC721 tokens on the blockchain

My question can be rephrased as: how does https://etherscan.io/tokens-nft work? Does they analyze every transaction data? The NFT tokens listed there doesn't implement the exact same ABI, is there ...
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1answer
82 views

How ERC20 and ERC721 deals with confirmation level

a smart contract store the internal balance per owner. when we transfer tokens from Owner A to Owner B, we update the internal balance sheet. but the internal balance sheet is a most recent snap shot. ...
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1answer
291 views

Two ERC721 tokens that refer to the same metadata

This is a question about the ERC721 interface. I understand that the tokens are non-fungible and guaranteed to be unique to a specific account (owner). One possible way to use ERC721 tokens would be ...
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724 views

mint method usage in ERC721 token implementation

What does the internal method call _mint(msg.sender, tokenId) really do in the background when used with ERC721 token implementation?
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How can there be a balance for an ERC721 contract?

Look at this implementation, I can see that ERC721 contracts keep track of an owner (identified by its address) for each single token (identified by its token ID, a 256 bit number): mapping (uint256 =...
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Should I checkAndCallSafeTransfer while creating NFT?

As per erc721 a good practice during transfer of an NFT is to use 'safeTransfer()' which calls: checkAndCallSafeTransfer of the IERC721Receiver interface. My question is, when creating a new ...
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1answer
135 views

Is it a good practice to create a new ERC721 NFT as needed?

I'm prototyping an asset management system using private blockchain and one of the main event is adding a new asset to the system. I was thinking about creating a new token when the asset is added to ...
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1answer
127 views

ERC725 adopting/extending ERC721 non fungibility attribute for unique decentralized identifier (DIDs) [closed]

Like the ERC20 standards, which is a great standard, I am imagining a future where there will be full of erc725 based token/identities. For decentralized identities to be unique, is there some way to ...
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296 views

ERC721 Metadata

Regarding the metadata URI extension - I don't think it should be required that each token ID has an individual metadata URI. I think there should be a globalTokenURI state variable that can be ...
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431 views

How do ERC721 tokens get created on private blockchain?

I'm creating a prototype using solidity for asset tracking where I need to create a new token for new items that are being added to the tracking system. I have gone through all possible tutorial on ...
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2answers
872 views

Proper way to implement “buyable” ERC721 tokens

I have a contract that implements the ERC721 interface, and I want to allow token owners to set their tokens as "buyable", so that any other address can buy their token without any action on the part ...
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1answer
1k views

“Error: sender account not recognized” when calling transferFrom() on an ERC721 contract

I am having an issue transferring ownership of an ERC721 token to a deployed Holding contract. The error I’m getting when running truffle test is the following - Error: sender account not recognized ...
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2answers
158 views

Is ERC721 an appropriate standard for managing licenses?

In my example scenario, I have an e-commerce dApp where e-books are sold. I originally thought that I could represent licenses to access these books using non-fungible tokens (NFTs) through the ERC721 ...
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1answer
498 views

DeclarationError: Identifier already declared. Two imports import the same ERC721 contract

Im building a contract that uses two contracts that both use the ERC721 zeppelin contract, when I import the two as such: import nonFungableWidthAddedFunctionality1.sol; import ...