Questions tagged [erc-721]

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

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2answers
381 views

Conformance test suite for ERC-721 smart contracts

Entities like Open Zeppelin offer "well tested and audited" (I'm paraphrasing) open source Solidity code for common patterns such as ownership, ERC20 tokens, etc. Are there any such entities (or just ...
6
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1answer
365 views

creation ERC721 error: Transaction failed, invalid address,

I would like to learn how ERC721 token works. I found some sample contracts online and tried to use remix and Ethereum Wallet to deploy the contract. The compile was fine but failed in the creation. ...
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2answers
559 views

Can erc721 belong to another erc721 token?

I learnt somewhere today that an erc721 token doesn't have to belong to an account, it could belong to another erc721! How can this be implemented? where can I read more of this? Thanks
5
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2answers
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 ...
4
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1answer
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 ...
4
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1answer
622 views

Why are the transfer and approve functions payable in the ERC-721 spec?

In the ERC-721 spec interface, the functions safeTransferFrom, transferFrom and approve all have the payable modifier. What is the reason for this? As far as I can tell, none of these functions ...
4
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1answer
4k views

How to create your own ERC 721 NFT token [closed]

I am trying to create my own ERC-721 non fungible token and unable to find any docs, basic code and how to deploy it on a testnet. Could someone share the official specification and an example of how ...
4
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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 ...
4
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1answer
725 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?
3
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3answers
446 views

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.
3
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1answer
811 views

Inheritance of constructor [duplicate]

Why does warning appear with inheritance of constructor? contract MyToken is ERC721Token{ function MyToken(string _name, string _symbol) ERC721Token(_name, _symbol) public { } The content of the ...
3
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2answers
406 views

ERC-721 safeTransferFrom is overloaded?

According to ERC-721 interface the function safeTransferFrom seems to be overloaded: function safeTransferFrom(address _from, address _to, uint256 _tokenId) public; function safeTransferFrom(address ...
3
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4answers
458 views

Non transferrable ERC721 token?

Is it possible to create a non transferrable ERC721 token? For whatever reason that some tokens I intend not to be transferrable, could I perhaps implement transfer in such a way that it could read a ...
3
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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 ...
3
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1answer
707 views

Why we can not add erc721 tokens in wallet?

I have created an erc721 token and when i try to transfer it from one address to another address that transaction is not visible on etherscan, moreover tokens are also not visible in mew or metamask? ...
3
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1answer
178 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 =...
3
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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 ...
3
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1answer
636 views

What's the point of ERC721Receiver.sol and ERC721Holder.sol in OpenZeppelin's implementation?

I'm studying OpenZeppelin's ERC721 token implementation and I'm having a hard time making sense of ERC721Receiver.sol and ERC721Holder.sol and how they relate to eachother. In the file ...
3
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1answer
1k views

I need help writing a working ERC 721 contract [closed]

I have been unable to write a working ERC 721 contract.Can someone help me with a sample ERC 721 contract that works? I have been learning for about a week now and I haven't made much progress.
3
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2answers
290 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 ...
3
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1answer
96 views

Issue in ERC721 token transfer to contract address

I am using ERC721 implementation for NFT tokens. I am testing the transfer functionalities in ERC721. `transferFrom(address _from, address _to, uint256 _tokenId)` `safeTransferFrom(address ...
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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 ...
3
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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 ...
3
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1answer
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 ...
3
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1answer
554 views

How to track ERC721 token transfers?

Wallets and etherscan can track ERC20 tokens an account owns, but are there plans for them to track ERC721 ownership?
3
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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 ...
3
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0answers
92 views

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 ...
3
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0answers
116 views

What Are Good Specific Reasons The onERC721Received Function Returns A Magic Value?

The ERC721 standard says the following: The onERC721Received function specifically works around old deployed contracts which may inadvertently return 1 (true) in certain circumstances even if they ...
2
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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 ...
2
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2answers
62 views

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 ...
2
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1answer
149 views

Execution of ERC721 Token

I have a Node-js application where cards are generated with unique number (ID11234). So I am planning to map a token for each card. In order to get uniqueness, I went through some of the documents, at-...
2
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2answers
549 views

How exactly is ERC721 tokens non-fungible?

What makes them unique as compared to the ERC20? Is it the owner's address as included in the form of token id? So what makes them unique is the historical chain of addresses attached to it?
2
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1answer
253 views

How to detect Ethereum ERC721 token

I have read the EIP abount ERC165 that is enable us to detect which interface is implemented in a contract. However, I found that some ERC721 tokens are a little bit diffrent from others, like ...
2
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2answers
101 views

How to guarantee IPFS file access based on Non Fungible Token ownership (or security)?

The file is too big to be stored on the blockchain, so it is stored on IPFS. Only the person who owns a unique Non Fungible Token (or a Security Token) can access it. Of course I can encrypt the file ...
2
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1answer
27 views

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 ...
2
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1answer
19 views

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/...
2
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2answers
28 views

Is there a way to be notified when ERC721 is deposited?

We are coding a contract that will work with ERC721 tokens, basically a Plasma Root Chain contract. We need this contract to do some work whenever it receives a new ERC721 token from a ...
2
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2answers
126 views

ERC721 Token - Burn and mint again

I didn't try yet, but let's suppose the following: I have an ERC721 contract token with a total Supply of 101 My contract can mint and burn The first token has id 0 and the last one has id 100 I ...
2
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1answer
60 views

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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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 ...
2
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1answer
286 views

Does each ERC-721 token have its own address?

I'm trying to create NFTs (non-fungible tokens), but I don't quite understand this part - is each token its own contract? or are all of them stored in the NFT equivalent of a 'balances' mapping in a ...
2
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2answers
129 views

ERC20 Interfaces overwriting ERC721 functions - Possible to adhere to standard?

Is it possible to have a contract that both generates and manages its own NFT according to the ERC721 Standard, and is able to make calls to outside ERC20 contracts? My contract currently inherits the ...
2
votes
1answer
323 views

Why does an ERC721 contract need to conform to the ERC721 and ERC165 standard?

Reading through the EIP for ERC 721 I notice that it is required to implement 2 different interfaces. Why is this? I noticed this portion in the documentation, but I think some clarification is ...
2
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4answers
231 views

Is it possible to obscure the owner of a non-fungible token?

Basically, I'd like to have unique records which can be transferred between parties without anyone knowing who owns a particular record until a transfer occurs, at which time only the recipient can ...
2
votes
2answers
376 views

ERC721 ownedTokens array length limitations on owners with thousands of tokens

In the ERC721Token contract, I am wondering the limits of: mapping (address => uint256[]) private ownedTokens; I am interested in providing functionality for users to potentially have thousands ...
2
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3answers
72 views

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
2
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2answers
75 views

Can hd wallets have different withdrawal permission levels?

Specifically, is it possible for a wallet to have a key which can spend an ERC721 collectible, but its child keys not?
2
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1answer
494 views

Trying to mint 721 tokens from external contract gives invalid opcode

I'm trying to build a second layer to erc721 nft. The problem is: I believe totalsupply is not in the proper format, but I'm not sure how to get totalSupply to be a uint passable into mint(). If I ...
2
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2answers
21 views

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 ...
2
votes
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=...