Questions tagged [erc-721]

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

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Temporarily ownership and Revokable ownership of NFT

Is NFTs allow to "temporarily own by a receiver" and the issuer can "cancel ownership of the receiver" or "directly assign it to a new receiver without burn existing NFT"?...
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Not quite ERC721 or ERC21

I have a problem that I'm really stuck with so I'm coming to the experts:) I have a personal project I'm working on. I'm minting tokens in large batches, once a condition is met, a new batch of tokens ...
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Solidity - Proper way to Import Contracts

When importing one Solidity contract into another, what’s the difference between importing it and accessing it using the is keyword, vs. importing it and just instantiating an object of it? Here’s ...
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retrieving web3 contract.ownerOf NFT ERC721

I'm playing around with web3 and frontend trying to read something off the ethereum blockchain. What i wanted to do is to verify the owner of a NFT (erc721). I've used this piece of code here that ...
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ERC1155 per token variables

I want to create an NFT that can mint different character types and multiple clones of each type. The clones within each type will start with same metadata, but each individual token should have its ...
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Why is the allowance 10**8 inside the test but equal to zero in the smart contract?

I'm running this test: def test_mint(prf, exValue, web3): wBtcAddress = "0x2260FAC5E5542a773Aa44fBCfeDf7C193bc2C599" ABI = [{"constant":True,"inputs":[],"...
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Metamask RPC error -32603… {“error”:“revert”,“program_counter”:6758,“return”:“0x”}

I have a dApp that leverages ERC721 contract which allows users to upload images onto IPFS and transfer them to each other. User A can upload images fine and transfer them fine to User B. Once ...
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how to set tokenid in erc721 openzeppelin? [closed]

First of all, sorry if I'm asking an obvious question. In ERC721 openzeppelin API, to manage a token you always need to refer to a tokenId. Are you supposed to define a global variable, or a mapping ...
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Solidity Integration of Multiple Contracts and a Library

I'm trying to understand the correct way to Deploy and then Import multiple Smart-Contracts and a Library when creating one big project. As an example, the project will have the following Library and ...
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ERC 721 Transfer Event vs. Sale Event Detection

When it comes to working with ERC721 Tokens, is there a way to figure out if a Transfer event was emitted due to the actual sale of a Token as opposed to the mere transferring of one? To be clear: it'...
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How can I determine which smart contract belongs to which vendor/app/etc. I am interacting with?

Rarible lists (on https://rarible.com/contracts.txt): RC721Sale Contract - 0x131aebbfe55bca0c9eaad4ea24d386c5c082dd58 ERC1155Sale Contract - 0x93f2a75d771628856f37f256da95e99ea28aafbe ERC721 Nonce ...
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Sales Transactions in Ethereum [closed]

I am creating a Dapp for ERC721 NFTs. To execute a sale of an NFT from one user to another on my smart contract, I am calling the _safeTransfer function of openzeppelin from within another external ...
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Solidity Multiple Contracts and Inheritance issue

My smart-contract has gotten bigger than the 24K size allowed by Ethereum, so I had to break it up into smaller contracts. I then had to facilitate all sorts of inheritance and importing between these ...
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ERC721 `safeTransfer()` chain of events

When examining OpenZeppelin's library of contracts for ERC721 Tokens, you'll find that all tolled, there are literally five flavors of the transfer method, as follows: transferFrom(from, to, tokenId) ...
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Is it possible to burn an NFT (ERC20 or ERC721) from other provider/creator?

I want to create a wallet/gallery for NFTs and I was wondering if it could be possible for the user to send NFTs made in other providers/minters to burn in my platform. The thing is that I want to ...
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ERC721 _holderTokens

The ERC721.sol provided by OpenZeppelin has a variable _holderTokens which is private. If I am writing my smart contract which inherits from ERC721.sol, is there any way to make that variable public ...
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TypeError: different number of components either side of equation

I am working on a project using ERC721. Code below pragma solidity >=0.4.21 <0.7.0; import "@openzeppelin/contracts/token/ERC721/ERC721.sol"; contract Sketch is ERC721 { string[] ...
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ERC721 Token Transfers and Approvals

ORIGINAL POST (EDITED POST BELOW): I keep getting the following error in my ERC721 Contract: “ERC721: transfer caller is not owner nor approved” This happens when I’m trying to buy a Token that has ...
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Calling “balanceOf” in a contract from another contract that imports it. Expected 1 Got 0

I have an ERC20 contract that calls BalanceOf in a ERC721 contract; In my ERC20 contract; import "./NFT.sol"; contract ERC20 { NFT public nft; constructor (NFT ...
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How to show erc721 NFT card images in compatible wallets?

I have created an NFT and now I want to add some metadata e.g card images, that shows in a compatible wallet like trust wallet. What step is needed next?
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Storing ERC721 metadata on IPFS

I wanted to store the metadata of my ERC721 tokens on IPFS. Currently, I am inheriting from OpenZeppelin ERC721.sol contract, and I saw there is a tokenURI function which returns the URI of the ...
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164 views

Updating ERC-721 Token's Metadata after it was Minted

Is it possible to somehow update an existing ERC-721 Token's MetaData after it was already minted? Let's say we've created a Knight character for a game - by minting an NFT for it, and 3 months later ...
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187 views

ERC-2309 Minting Multiple ERC-721 Tokens in one Transaction

Anyone know how to work with ERC-2309? It's an extension to the ERC-721 Token standard and it's supposed to make it possible to mint a large number of ERC-721 tokens (meaning 100's or even 1000's of ...
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Can one ERC721 have two type NFT?

I am new to smart contract, I have to make NFTs so I am following ERC721 standard, but I have to make two types of NFT NFT1 = {prop1, prop2} NFT2 = {prop3, prop4} so can I have two type of createNFT ...
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Pull metadata from ERC721 contracts

what tools/services would you recommend for pulling metadata from ERC721 contracts? It seems like it's going to be a huge hassle to return the metadata directly from the blockchain. Any clever ideas?
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Trouble using delegatecall to pass msg.sender to another contract

I'm trying to mint an NFT token in contract B by calling a method on contract A, but I want msg.sender (in contract B) to be the address that calls the function on A, not contract A's address. I ...
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Why is the ERC721 metadata limited to images?

Why is the ERC721 metadata JSON Schema limited to images? If I specify a file other than the image, does it cause an error when issuing the token? If it can be issued, what will be sacrificed? (e.g., ...
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safeTransferFrom is undefined in buidler test

I have started using buidler for testing/compiling my contracts. In one test i have setup a scenario that a owner attempts to transfer a token to another wallet address. My contract is inheriting from ...
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Take a percentage of msg.value on ERC721 transfer

I want to transfer part of the value paid to an address whenever an NFT is traded. If the value is 0, then nothing is transferred. My original idea was to override the transfer function in ...
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Can a contract address have both ERC20 and ERC721 transactions

Some addresses on Etherscan like this one show both type of transactions (ERC20 and ERC721) on Etherscan. So, does that mean that both standards can be implemented at the same time for a token?
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Modifying erc-721 transfer

Say I want to take a cut of an NFT each time the token is transferred. If I were to change the openzeppelin erc721 transfer function to transfer 1% of the NFTs holding to myself, can that standard ...
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Functions that are used for token transfers for ERC20 and ERC721 tokens

Let's suppose there is a contract address A of an erc721 token B. If I want to monitor all of its transfers from A to another address say C then should I only filter the Transfer function or should I ...
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Where can I find full ERC 721 example programs?

I am building a program with an ERC 721 token. My code runs without using the standard components provided by Open Zeppelin IERC721. Now I want to adapt it to the ERC 721 standard. Unfortunately the ...
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Read and write private variable from child contract

I have a contract MyContract is ERC721. MyContract needs to concatenate a string with an existing token URI using this function: string(abi.encodePacked(_tokenURIs[_tokenId], _URI)); Problem is all ...
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Enforcing a limit on ERC721 tokens held by an account

We are providing a Gnosis multisig wallets to our users and a market place where users can purchase/sell/transfer ERC721 tokens with other users. The ERC721 contract will also have a Blacklist ...
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Passing constructor arguments from child contract to parent contract

The ERC721 standard contract requires a token name and symbol in its constructor. I have inheritance pattern that looks likes Contract A is B and Contract B is ERC721. If I want to set my token name ...
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Why doesn't CryproKitties contract use Enumerable.sol?

I am going through the Cryptokitties code, which does not include the optional Enumerable contract, but the KittyBase contract basically declares equivalent indexation and functions. Why did ...
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Identifying ERC-721, ERC-777, & ERC-223 Contracts in the EVM via eth.getTransactionReceipts(), etc

Is there any specific way of identifying ERC-721, ERC-777, & ERC-223 contract events under the EVM, specifically under the eth.getTransactionReceipt() function? I know there's a way for ERC-20 ...
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Possibilities of ERC721 image generation [closed]

What image generation techniques could you suggest for a DApp game that utilizes ERC721? I know that CrypoKitties has a unique DNA sequence and different pieces of the sequence correspond to the ...
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When and where do I set ERC721 tokens' data?

I am currently working on a smart contract to sell ERC721 tokens. I understand that my code should have a function that allows me (the owner) to mint a token and add it to a list which stores all the ...
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Does a symbol have to be unique in ERC721? How to find out a unique symbol?

As per the ERC-721 contract on OpenZeppelin, you can create a token with this constructor: constructor(string _name, string _symbol) public {} Does the "_symbol" have to be unique across the ...
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Obtaining ERC721 interface IDs

There's a related question here ERC721: Interface ID Registration but I couldn't get the answer I need from there. In the OpenZeppelin ERC721 basic implementation, there's this part: // Base URI ...
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127 views

How to query Cryptokitties metadata from Etherscan

I;m trying to query a Cryptokitties token metadata from Etherscan and I need to give two values: _tokenId (uint256) and _preferredTransport (string). What are possible value for _preferredTransport?
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How do exchanges work internally?

Because EVM cannot watch events, we cannot send a token to an exchange and immediately get back some other token (EVM just does not "know" when it was send a token). As far as I understand, this is ...
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ERC721 Token abstract contract or an interface and cannot be deployed

after reading many post i can't found the issues about this Smart contract who compile but it think i miss something about the inheritance and the Abstract contract. This is the SC : // solium-...
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How to issue new ERC 721 tokens for each individuals with different name and symbol

I'm working with an app where different users can create their own ERC721 tokens by passing token, symbol total supply etc. Currently, the code is creating the token, but it has common name only. ...
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Which token standard should be use to create different tokens for different users?

I have read several differences between fungible and non fungible tokens. It cleared my few doubts though, I have few more remaining. I have requirement to create a platform on which users can ...
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Difference between ERC 20 and ERC 721 transaction receipt

I want to fetch certain transaction logs from a local ethereum node. For that, I need to identify how to differentiate between ERC 20 and ERC 721 transaction receipts. From what I saw on Etherscan, i ...
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When to use nonfungible tokens and possibility to interchange tokens with different standards

I'm little bit familiar with Blockchain and ERC-20 standard. Now I started learning about ERC-721 and having a lot of confusion. Let's take an example of music artist token platform. Any music ...
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Difference between method id, event id and ABI signature for event

I am confused as to what is the difference between method id, event id and abi signature. I got the abi signature of a token transfer function according to the following web3js function const ...

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