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Questions tagged [erc-721]

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

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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?

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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Write a Function to Exchange ERC721 Tokens

How can we exchange Exchange ERC721 Tokens between two addresses? What would be contract function to write with oppenzeppelin 2.0 and truffle. Implemented exchangeStars() function in contract: ...
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1answer
15 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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18 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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1answer
20 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
16 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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2answers
23 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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0answers
21 views

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
22 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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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
29 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
61 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
32 views

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
36 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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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
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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
57 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
47 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
28 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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ERC-20 Token Transfer Error (Unable to locate Corresponding Transfer Event Logs), Check with Sender when trying to send ERC721 tokens

I am trying to transfer ERC721 tokens from one account to another on Ropsten network. I do this by creating raw transaction, signing and broadcasting transactions I created the transaction this way {...
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1answer
44 views

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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1answer
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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
130 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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0answers
79 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
76 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
34 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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1answer
209 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
50 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
164 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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1answer
194 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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1answer
72 views

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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0answers
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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
69 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
73 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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1answer
151 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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1answer
179 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
418 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
401 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
107 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
189 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 ...
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1answer
27 views

When extending a contract how to call the external constructor and pass parameters?

I have the following contract import "zeppelin-solidity/contracts/token/ERC721/ERC721Token.sol"; contract Contract is ERC721Token { function Contract(string _name, string _symbol) public { ...
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1answer
44 views

erc-721 erc-20 solidity code check effects interaction pattern

Where can one locate a formally verified ERC20/ERC721 solidity code/template that adheres to security design patterns such as check effects interaction patterns?
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1answer
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Use of the “indexed” keyword and token standards

Long story short, while making a blockchain crawler that would extract all ERC20 transactions I learned the hard way that ERC721 has the same "signature" as ERC20 (and probably many others that I ...
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0answers
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How are ERC-721 protocol tokens different from Ardor assets? Is there a pro/con data sheet?

ERC-721 protocol is used to create unique tokens like crypto kitties, but I'm curious has anyone compared it to the Ardor Ignis singleton assets as it seems like it does something similar. Is there a ...
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365 views

Transfer an ERC721 Token from another contract

I'm getting a revert when trying to transfer a token from another contract, I'm calling the function from an Auctions contract, for example, when the max bidder claims the reward they get the token ...
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1answer
20 views

Truffle test failing due to different data type than expected

I am using truffle and ganache to make a token demo for myself. I'm following this guide then making my own changes according to my project. When I try running tests to verify that my contract is ...
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1answer
327 views

List ERC721 tokens owned by a user on a web page

Let's say that I have an ERC721 (NFT) contract that represents a set of playing cards. Is there sample code out there that shows listing all of the tokens of that ERC721 contract that a user owns on ...
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1answer
33 views

Does ERC-20 or ERC-721 compliance mean anything of consequence? Are these standards necessary to use

Why do we have to use these standards? Is complying with these standards a necessity if we want our token to be listed anywhere? If our token doesn't fit within the listed standard, can we still have ...