Questions tagged [tokens]

A token is a transferable, divisible object on the blockchain, such as a subcurrency or a prediction market share.

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How can I find the block where a user enacted a certain event on a contract?

I'm trying to build a web3.py program to take in a given user's address, and return the amount of ETH traded since they added liquidity to a Uniswap exchange. Uniswap is a smart contract on the ...
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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, ...
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Why am I getting a Parse Error in my smart contract after the constructor?

I'm writing a token sale smart contract & my original error was my function had the same name as the contract and I changed it to a constructor because the contract cant have the same name as the ...
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1answer
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Etherscan api for Ropsten testnet

I found this endpoint is to obtain the token balance from Ethereum blockchain, however, I noticed that this function doesn't work on Rospten network. Please advise https://api.etherscan.io/api?module=...
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How can I collect the tokens inside smart contract that people will send accidentally?

I have an ERC20 token XYZ smart contract created. People will send certain amount of tokens back to the contract address to initiate certain functions. I just want to know that what will happen if ...
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ERC20 transfer showing as 0 but log shows different

Checking the transaction https://www.etherchain.org/tx/e12af4940879c634a63d2c9629449695e07650a4e419e5822ddb18d8469e9948 anyone can check there were 3 DigixGold token transfers. These transfers are ...
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What will happen to legacy smart contracts when Ethereum 2.0 is released?

Most importantly, ERC20 and ERC721 tokens. Will they be migrated to the new chain? Will migration only be optionally possible for contracts with an owner? What about contracts which rely on proof of ...
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20 views

ERC20 - Approve & TransferFrom not working

The getTokenBalance function seems to retrieve data from the ERC20 contract just fine so I don't think there is an issue with how I'm using the interface. Additionally, I also tested out separating ...
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Ethereum Contract Scalability (Single vs Multiple Contracts)

I am writing a token swap contract on Ethereum Blockchain to manage ERC 20 token swap in an exchange. The Questions is that in terms of scalability, which of the following two options would be better ...
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how to integrate USDT erc20 token to make transfer and check balanceof?

I want to integrate USDT token to make transfer and check balance of USDT in my java with the use of web3j, how can i accomplish this? i able to create wallet and use of ethereum, but i dont know how ...
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Zepellin Crowsale buyTokens error

I'm trying to use the buyTokens function of the Zepellin Crowsale interface, but this gives me an error, without any log to be able to debug contract TokenA is MintableToken, PausableToken, ...
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token tracker not found in ropsten

Generate a token called ye22, and deploy it in the ropsten test block, the contract is generated, the tokens are sent to an owner, but this token is not visible in ropsten, only the contract This is ...
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The rank of Bittrain coin [closed]

I would like to but a bittrain coin. I have gone through the list and I cant find it ranking. Can I buy it on this platform?
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How to create smart contracts and tokens without using any cryptocurency?

I am new to Blockchain and I have read to create tokens smart contracts are required and to create a smart contract,ether is required. I wanted to know is there anyway I can create tokens without ...
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23 views

How to authorize multiple contracts issue the same ERC20 token?

I have a physical product to sell. I want to have a digital asset representing each unit of my physical asset. I have created an ERC20 token contract and each token represents a unique instance of the ...
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how to implement erc1400 standard?

I am trying to learn about erc1400 and its implementation but couldn't find any complete implementation guide. Can someone points me to relevant links regarding erc1400 complete end to end ...
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1answer
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How to request tokens from msg.sender within contract function

transferring ethereum from the user of your smart contract is simple enough, you simply use msg.value and can use this within your contract's functions. But doing the same thing with tokens is a bit ...
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Is it legal create an algorithmic trading cryptocurrency fund for social groups around the globe to pool in their money?

Is it legal create an algorithmic trading cryptocurrency fund for social groups around the globe to pool in their money? What is the viability of this project in terms of regulatory compliance?
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Token migration and IDEX smart contract problem

During a recent token migration from token A to token B, a large number of token A were held by a number of people in an IDEX address (where it was ready to trade). The IDEX address is part of a smart ...
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28 views

can etherscan.io show local ganache transaction details?

I am purchasing tokens on my sample Dapp with ganache-cli account using metamask. Metamask shows the confirm message and deduct the ether from total balance but in token section it still not update ...
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How to set and get marketprice of token in contract? [closed]

I am building a simple erc-20 token. I don't have an idea as how token price is setup. However, I need to get my token's market price inside another contract. If you see this example of token BOMB, it ...
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1answer
50 views

Custom token showing balance of 0 in MyEtherWallet

I made a new token on the Ropsten test network. Here's the contract address: 0x801fd9c17087ec868dc8540055b7ea3cb6dbbe34. When I followed the instructions to add this custom token to MyEtherWallet (by ...
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error: VM Exception while processing transaction: revert SafeMath: subtraction overflow on migrating crowdsale conract

I am developing the token sale Dapp using openzepplin-solidity version 2.3. While migrating, I got the following error. Returned error: VM Exception while processing transaction: revert SafeMath:...
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Smart-contracts referencing each other [duplicate]

How would one retrieve these three addresses in the "Knot" smart-contract? I am very new to this, and would like to know whether this is even possible. The "Knot" contract should be able to reference ...
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36 views

What should gas prices be for sending out tokens?

I constantly get failed transactions when sending out tokens like USDT using metamask. I have my gwei set at 10 and the gas limit at 21000. I even tried gas limit set to 51000 and it still fails. ...
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28 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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2answers
29 views

Which erc token to use?

I wonder someone could give me some advice. I am planning to work on a Ethereum project with a Solidity smart contract. The smart contract should contain tokens which can be earned by a person by ...
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ERC-20 Token Transfer Error (Unable to locate Corresponding Transfer Event Logs), Check with Sender

EtherScan.io is showing error: The ERC-20 Token Transfer might have Failed (ErrCode: unable to locate corresponding Transfer event log), check with sender. Transactions are successful and the ...
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1answer
35 views

Get ETH and Token Balances of Wallet address

How do I get a simple and fast balance of ETH and all Token owned/stored within a wallet address? I have seen similar question and the closer answer was in this demo: http://wbobeirne.com/eth-...
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32 views

Wrong estimation of gas while contract deployment

I have a smart contract: pragma solidity 0.5.3; import "./ERC20.sol"; contract Transfer { ERC20 private erc20iface; address private _owner; modifier validOwner() { require(msg.sender == ...
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1answer
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Measuring elapsed time between user erc20 token transfers with lazy evalutation

So I'm learning solidity and wanted to make an erc-20 token after reading the solidity by example docs. Let's call the token T. I would like to measure the elapsed time between two transfers of an ...
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Is there an ethereum android wallet where I don't have to manually add in tokens I have and just auto detects it?

Using coinomi or even metamask on chrome is quite annoying as I need to manually add in tokens I have in my account and it doesn't auto show up. Is there an android or desktop ethereum wallet that ...
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1answer
21 views

Is Smart Contract of any ERC20 token is always available publicly

Is Smart Contract of any ERC20 token is always available publicly. If not complete, then what things are generally available,(for eg, except some sensitive information) And, if not any of them are ...
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Is there a token standard that allow for future minting and burning of tokens?

I am interested in an ethereum token with the functionality for an operator to mint new supply at any time. It would also be nice if the operator could burn supply explicitly rather than sending to an ...
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1answer
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Parser Error - Creating EIP20 Tokens

function transfer(address _to, uint256 _value) public returns (bool success) { require(balances[msg.sender] >= _value); balances[msg.sender] -= _value; balances[_to] += _value; emit ...
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1answer
80 views

Percentage calculation

I'm currently learning how to write smart contracts. While studying some code, I came across this line: ‭ uint256 a = value.ceil(basePercent); (with: uint256 public basePercent = 100;) Then one ...
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1answer
36 views

ERC20, how to calculate how many tokens for crowdsale?

If you look at this article, the total tokens for crowdsale is 100 tokens and defined in the code as uint256 public maxTokens = 100000000000000000000; how come 100000000000000000000 becomes 100 ...
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1answer
30 views

Code A Contract To Accept A Different Token (Other Than ETH)

I'm developing a DApp for Decentraland that will accept payments in their ERC-20 token MANA. How can I code a smart contract to accept a token other than Eth? How can msg.value know the value of a ...
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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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29 views

use the caller of the wrapper function to call the inner function

Suppose, I have 2 contracts A and B: contract A{ function someMethod() public{ // Something happens here } } And contract B containing its instance and its wrapper function ...
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What is the latest implementation of approveAndCall() - Solidity ˆ0.5.0

Just curious for some background on approveAndCall() 1) Is it initially an ERC223 method ? or is it officially part of the ERC20 interface ? 2) Also Im working with an old contract so Im wondering ...
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1answer
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How do we communicate with contract functionality which is deployed in public test network using web3j [closed]

I would like to write a wepapp for security token contract which is deployed in public Ropsten Test Network using web3j. Need some idea. Thanks in Advance
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How and Why other should buy and sell my ICO token? [closed]

When I invest or create a token, I am hoping someone in the future will want to buy it at a higher price. Why would anyone buy my tokens to use the platform if the price of the token keeps increasing ...
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1answer
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How can I wait if it's not possible in smart contracts? [duplicate]

From my understanding, waiting in a solidity smart contract would create a total disaster for the whole Ethereum's blockchain. I can see in some circumstances that solidity offers block.timestamp ...
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1answer
46 views

How to swap tokens?

Say I have a X token and Y token and I want to swap X tokens in exchange for Y tokens. How can i do that? Its like during crowdsale, instead of using ether to buy the Y token I want to accomplish the ...
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1answer
103 views

Web3 Contract.balanceOf is not a function

I have read this helpful SO answer about sending ERC20 contracts, but it seems that the Web3 docs and API have changed dramatically since then. I am trying to get the balance of a smart contract using ...
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1answer
41 views

Create custom mobile wallet for my two ERC20 Tokens

I have two ERC20 tokens that I created on Ethereum. I would like to know if it is possible for me to create a mobile application that will allow my users to check their balance (for tokens) and ...
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Manage a whitelist

I can see security tokens solutions like PolyMath keep the whitelist on the contract and allow transfer only after checking the sender and the receiver are on the whitelist. What I'm not clear about ...
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Help with ERC20 Contract

I sent tokens to my contract address instead of to my myetherwallet address from an address that the tokens were previously sent some time ago. Now I have no access to the amount sent to this address. ...
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1answer
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How are people using ERC20 to tokenize assets

Hey guys been looking a lot into tokenization of assets wondering how this is possible with ERC20 (Seeing a lot of people use it and keen to understand) how would you represent an asset with each ...