Questions tagged [erc-721]

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

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ERC721TokenReceiver, assuming that transfer function exists?

When trying to find out if a contract implemented onERC721Received from safeTransferFrom function, are we just safely assuming the contract has all the erc721 related functionalities? such as transfer,...
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bytes data param in safeTransferFrom

In ERC721, safeTransferFrom has bytes data parameter. function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) public; how do I send data (is it in hex format?) and what ...
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What does mutability guarantees mean in erc721

Some functions from ERC-721 interface contain payable modifiers. function transferFrom(address _from, address _to, uint256 _tokenId) external payable; I was wondering why it is payable and found ...
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Is there a reason why minting is excluded in erc721 interface?

So the EIP-721 standard says, Creating of NFTs ("minting") and destruction NFTs ("burning") is not included in the specification. Your contract may implement these by other means. interface ...
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others accessing setApprovalForAll ERC721

While I was skimming through open zeppelin's ERC721BasicToken.sol I came across a problem. When setting the approval of a given operator function setApprovalForAll(address _to, bool _approved) ...
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ERC721Enumeration: DeclarationError for tokenOfOwnerByIndex(address owner, uint256 index)

I am new to the smart contract and please let me know why I have the error shown below. I compiled with the command, "truffle compile". I did not make any particular edits to the original contract ...
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2answers
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ERC721 exchange logic

I'm trying to allow NFT holders to sell their tokens by listing prices (ETH) and allow others to buy those listed tokens. I used openzeppelin and succesfully implemented and tested my token creation. ...
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24 views

Create multiple tokens for a unique property

here is the idea: we assign a set of unique tokens to a company and then we allow people to buy some tokens and get partial ownership of that company. How can I achieve this? I was thinking of ...
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ERC721 Metadata and Items

i'm new to ERC721 tokens so this may be a stupid question. Following the Opensea docs and other docs (for example openzeppelin ones), I just create a simple ERC721 token that i called "avatar" which ...
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23 views

How to show inventory tab on etherscan

Sorry, i'm newbie about ERC-721. I have deployed my contract and verified it. https://ropsten.etherscan.io/address/0x677f76d276355c382da948d2476da06cf5dc6219 But I don't see inventory tabs like other ...
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What is the current distribution of ERC Token Standards in the top 100-1000 most active token contracts?

From ERC 677 Motivation ERC20 requires a multistep process for tokens to be transferred to a contract. First approvemust be called on the token contract, enabling the contract to withdraw the ...
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40 views

Transfer erc721 token to another address

I'm currently using transferFrom / safeTransferFrom to transfer the token to another address but I encounter this error. Error: Error: invalid address (arg="to", coderType="address", value="...
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ERC721, Token name and symbol not shown in etherscan

I have created a simple token with ERC721, but etherscan not show my token name and symbol, why? this is my contract I deploy with this code Result on etherscan No token name and symbol showed, is ...
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Why should I use an ERC-721 token to store data instead of a Smart Contract

Taking CryptoKitties as example, I'm sure it's possible to achieve the same concept of Crypto Collectable creating new kitties as Smart Contracts instead of using Tokens. Which would be the ...
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Is there a maximum/optimum amount of ERC-721 that can be issued per contract?

Take a role playing game as example in which players are allowed to create any number of characters (each one defined by an ERC-721 token). What would be the consequences of having more than 10 ...
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ERC721: Interface ID Registration

Why we need to register Interface ID in ERC721 token. I was just going through the openzeppelin-solidity erc721 code and curious to know that why we need to use this. That interface id register code ...
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Can you add a link to a ERC-721

I would like to get your though about what would be the best way to encapsulate a document in the blockchain. What i would like to achieve is that 1 token = 1 document, this token isn't divisible, and ...
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How do I send NFT assets (ERC721 Tokens) from my Ethereum wallet to someone else?

I want to send my ERC-721 to my friend. Fast. Any suggestions?
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ERC721Token super._mint calls addTokenTo from the top level implementation

Based on Shawn's answer, super._mint calls addTokenTo from the top level implementation (ERC721Token). How does this work? super._mint calls _mint from ERC721BasicToken reads line addTokenTo ...
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31 views

ERC721 how does tokenOfOwnerByIndex() list tokens owned by a user?

Per eip-721, there's an optional "enumeration extension". So what I did was I called balanceOf to get the number of tokens owned by the account and called tokenOfOwnerByIndex in a loop to get each ...
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20 views

Where can I find public and known ERC20-Contracts from existing ICOs

In order to list real live example code for ERC20-Token and Crowdsales at a talk about Smart Contracts I'm looking for such projects? Who can recommend me the real GOOD examples out there (and not ...
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52 views

Store ERC721 token metadata

I am new to ERC721 tokens so this may be a stupid question. I want to create my own ERC721 which can be integrated with opensea using the metadata, as far as I understand you have to store the ...
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Using geth Light Node to detect ERC-721 transactions

Is it possible to use a geth light node to detect incoming transactions executed via ERC-721 contracts? I have experienced being not able to get receipts using getTransactionReceipt in native and ...
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3answers
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ERC721 Tokens - Hold ETH in the token?

Would it be possible to create a ERC721 Token for say a game item, but I want the Token to basically have ETH inside the token, so that a user could destroy the token to reclai
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add fields to ERC721 tokens, still belongs to the standard?

if starting from the code of an erc721 token, I add fields beside the name, symbol and URI, is it still a token that respects the standard? Add in the contract, not in the JSON file. The most ...
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ERC721-OpenZeppelin: This contract does not implement all functions and thus cannot be created

I know there are already a lot of topics that deal with the problem but their solutions didn't work for me. this is the code: pragma solidity ^0.5.2; import "https://github.com/OpenZeppelin/...
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onERC721Recieved implementation

As per the ERC721 requirements, I have to implement onERC721Recieved. This is how I did it: function onERC721Received( address _operator, address _from, uint256 _tokenId, ...
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ERC721: How to get the owned tokens of an address

There is a balanceOf function, but it only displays one uint (the token identifier) I see most ERC721 tokens doing this so I am confused on how to view all owned tokens.
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ERC 20 or ERC 721 for my dapp?

I am currently making a game where you collect gear pieces and upgrade them. There will not be a 1-1 upgrade, but rather 3-1, meaning 3 items may or may not upgrade to 1. I am aware of the difference ...
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ERC 998 ERC 721 Top-down: Can child tokens affect the status of the parent

I'm trying to make a DAPP, which involves using an ERC998 Top-down. I want to introduce a status on the token, and status has 2 options (ACTIVE and INACTIVE) I was wondering, is it possible to ...
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1answer
48 views

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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44 views

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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39 views

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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1answer
63 views

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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64 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
250 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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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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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
171 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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60 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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193 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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131 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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589 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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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 ...