Questions tagged [erc-721]

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

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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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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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54 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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25 views

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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1answer
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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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40 views

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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22 views

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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104 views

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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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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1answer
54 views

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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ERC20 and/or ERC721

Consider the following scenario. A person owns a asset called "A". Now the asset is very high valued and unique but you can allow other persons to own a certain part of that asset. EDIT: Ownership ...
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Can an NFT (e.g. ERC721) simultaneously belong to two different entities, say an user Owner, as well as a user Custodian?

For example, on the blockchain say you own a ERC721 Car token at your wallet address, but you want to park it in the ERC998ERC721 top down composable Garage owned by your friend, while still retaining ...
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Smart Contract overview ERC-20 instead of ERC-721

I have created ERC-721 standard but on etherscan (Ropsten) it's still showing ERC-20 standard in overview Below are my contract code, please share your thought if I'm doing something wrong. contract ...
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all erc 721 tokens being collectibles

Considering all NFTs are unique, are all erc 721 tokens collectibles? I'm asking this because on the Etherscan website some NFTs have the collectibles tag and some do not.
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Unable to invoke smart contract function from Web3j contract wrapper

I've been learning about interacting with smart contracts through Android and the Web3j framework but have run into an issue. I'm trying to mint an ERC721 token and send it to an address but it doesn'...
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Api to get total transfer count of an ERC-721 Token

I want to retrieve the total number of an erc 721 token's transfers/ transactions. I couldn't scrape the transfers value from etherscan as well e.g. given here https://etherscan.io/token/...
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Confusion regarding total number of ERC-721 Tokens

I have two questions: 1) I want to retrieve the list of all ERC-721 tokens. The main block explorer for Ethereum which is Etherscan shows 2,883 ERC-721 tokens on its website https://etherscan.io/...
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ERC-721 - How to avoid that an updatable tokenURI becomes a vulnerability for token trust?

I understand that one can use the tokenURI field to add the address for an endpoint that returns meta data for the given token. Let's imagine we create a unique asset with tokenId = "1" tokenURI = "...
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2answers
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ERC standard: possible to set upper price limit for NFT?

Let's say I want to create a non-fungible token which represents a ticket to a venue. And I don't want ticket scalpers to buy tickets and resell these tickets for a higher price. It should only be ...
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Using a Non-Fungible token to gain access to a file

Please excuse me, I'm a layperson, not a programmer. At this time is there a way to issue NFT's to be used as a 'key' to gain access to a file on the internet? For example you create and sell an NFT ...
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138 views

How many projects are there which implement ERC1155 standard?

New ERC1155 standard which is thought to be an improved version of ERC721 and ERC20. But I see many projects still prefer ERC20 or ERC721 standards. If so, do you know any projects implementing ...
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224 views

Solidity bytecode not generated despite no errors

When does a compiler fail to generate bytecode for solidity? The code compiles entirely but both remix and solc js give proper abi but empty bytecode. The contract imports ERC721. Solidity contract: ...
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Cann't send token with looping function

Sorry, I'm a newbie on ERC721 token. Please help. I have deployed ERC721 contract in the localhost testnet. I use looping function for mint token and it works. But when I use looping function for ...
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Can we send tokens with data input? [duplicate]

Can we send tokens with data input? I did a bit of research on erc20 but maybe this is quite complicated. Will erc 721 do this?
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Self-destructing NFT (ERC-721) token [closed]

What I want to achieve is self-destructing token. For example I'd like to have some updatable TTL value assigned to my token. If TTL is reached the token should be auto-burned. What are the best ...
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48 views

Are there any good ways to express conditional ownership on ERC20 or ERC721 tokens?

I'm currently looking for any good ways to express conditional ownership on tokens. I look into approve function of both ERC20/ERC721 but, it seems that function may be disapproved by the owner and ...
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ERC721 - How to create many ERC721 tokens at a time

Is it possible to create many ERC721 tokens at a time? I saw this link. ERC721 - Create 1000 tokens in one function call But I don't get it. Please help me.
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gas required exceeds allowance when deploying ERC721token

I am trying to deploy Smart-contract(ERC721) on my private ethereum network. But I have this issue. Here is my genesis. { "config": { "chainId": 3333, "homesteadBlock": 1, ...