Questions tagged [erc-20-approve]
The erc-20-approve tag has no usage guidance.
149
questions
12
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4
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Is it possible to batch approve + transfer an ERC-20 token?
In our dapp, we currently have the following user flow:
Approve the Sablier contract to spend up to x ERC20 tokens
Transfer the x ERC20 tokens to the Sablier contract
This is not super bad UX, but ...
- 18k
6
votes
0
answers
290
views
Not able to use DAI's permit() function
I'm having trouble testing the permit() functionality from the DAI contract. I've read the documentation and a couple of other resources, although, I got the contract code and deployed myself a copy ...
- 1,423
5
votes
1
answer
3k
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Difference between Approve() and IncreaseAllowance() in ERC20 contract
Over the last few days, I have been looking up the best and clear explanation of the differences between Approve() and increaseAllowance() of the ERC20 contract. Still, I couldn't come up with a ...
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4
votes
2
answers
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What is the use case of transferFrom function in ERC20 token contract?
In @openZeppelin's ERC20 implementation here is the code for function transferFrom:
function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
...
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4
votes
1
answer
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Ethers.js - Error: invalid BigNumber string
I am trying to approve a larger amount of erc-20 tokens (it has 18 decimals).
await token.connect(signer).approve(contractAddress, BigNumber.from((1000*(tenToPowerOf18Digits)).toString())) :
If I try ...
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4
votes
1
answer
6k
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How to transfer ERC20 token to another contract and calling contracts function
I need to send an ERC20 Token from a contract to another contract and calling a function of the other contract at the same time.
I know how to transfer an ERC20 Token from solidity to another contract,...
- 43
4
votes
1
answer
3k
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What is the best way to use uniswap without router?
I just bought a scam token. The liquidity pool is still there but I couldn't sell because I couldn't approve the token in Uniswap. When I try to approve, the error "execution reverted: ERC20: ...
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4
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3
answers
1k
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ERC-20 token approval fails if amount is close to maximum balance
So I am using Wagmi, which uses Ethers.js under the hood. I have to approve the router address first in order to buy the other token.
It works when I use the exact or slightly greater amount than what ...
- 171
3
votes
3
answers
23k
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Fail with error 'TransferHelper: TRANSFER_FROM_FAILED' even approved in contract
I'm rying to swap some BNB -> Token, then swap it back, all in one solidity function. Here's my code:
interface IERC20 {
function approve(address spender, uint256 value) external returns (bool);...
- 251
3
votes
2
answers
2k
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Approve ERC20 token inside a contract function
I would like to understand why, approving an ERC20 token inside a contract function doesn't work.
Suppose that I create a function in my contract, that calls an approve for an ERC20 token for the ...
- 167
3
votes
1
answer
74
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Is it possible to allow a third-party relayer to spend ETH on your behalf?
With the ERC-20 standard, it is possible to approve a third-party relayer to spend the tokens on your behalf. This can be done by calling the approve function and providing a high allowance value, ...
- 18k
2
votes
1
answer
2k
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i am new to this, can someone steal my erc20 token with the Function approve()
I have been using yield Farming (YFValue) and I noticed when I accept the contract via MetaMask.
I set faming 500 USDT but in the contract the input was:
Function: approve(address _spender, uint256 ...
- 23
2
votes
2
answers
51
views
ERC20 without approve
Is is good practice if I have a custom-made ERC20 that takes its own tokens out of the user for doing other stuff?
I ask since doing it this way there's no need for the user to call approve() ...
- 934
2
votes
1
answer
59
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Transfer tokens to and from smart contract [closed]
I would like to have a new ERC20 token and one or two smart contracts to do automatic trade with specific cryptos.
Example: I can buy 1 token from the contract in exchange for 1 USDT.
I can sell a ...
- 123
2
votes
1
answer
960
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Current ERC20 approval best practices?
I've been reading some (old) discussions about the potential attack vector of using ERC20 approve (for example: https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729) but I've been ...
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2
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1
answer
3k
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How to interact with a smart contract without ABI
So I bought a scamcoin (I know). I have the contract and I've managed to decompile the bytecode. How can I interact with the contract to approve the token?
https://bscscan.com/address/...
2
votes
1
answer
2k
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How to approve user to spend all my ERC20 tokens?
In ERC20 we approve a user to spend our token and then they can spend as much allowed using transferFrom, but if the allowance limit exceed then I have to approve again, is there any way to allow them ...
- 319
2
votes
2
answers
565
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Approve many tokens with one transaction
I need the users to approve the ERC-721 token before the smart contract and transfer it to someone. the default "approve" function works fine. but I'm wondering how to approve many tokens at ...
- 205
2
votes
1
answer
1k
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Fail with error 'TransferHelper: TRANSFER_FROM_FAILED' Although approved
I'm trying to make a swap programmatically, I did the following approvals using ethers.js:
token0.approve(wallet.address, amount);
token1.approve(wallet.address, amount);
token0.approve(...
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2
votes
1
answer
61
views
Getting error ERC20: insufficient allowance even after the user approving the tokens. Need help with debugging
The following code is from a Stablecoin project.
To gain more context, please refer to this Github repo.
I've added a new function to the DSCEngine.sol name collapseDsc() which is responsible for ...
2
votes
0
answers
99
views
Use Brownie to send ERC20 tokens to a payable function with the amount of tokens as an argument to the function
I have the following AlgoToken contract:
interface StableCoin {
function balanceOf(address account) external view returns (uint256);
function allowance(address owner, address spender) external ...
2
votes
1
answer
41
views
Manage tokens on the behalf of to call a smart contract
I would like to transfer tokens to defi smart contracts on the behalf of a third-party.
I see no option apart from (1) the third-party to transfer to me directly (2) the third-party to pre-sign ...
- 21
2
votes
1
answer
2k
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"gas estimation failed" error using Uniswap. Can't fix it, please help
I can't sell alt-tokens back into ETH. This is an issue with multiple tokens, not just one and they all have very high liquidity ($Kabosu and $OHMI).
I immediately get the error 'gas estimation failed'...
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1
vote
1
answer
1k
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Usecase for approve and allowance functions of ERC20 token
Could you please enlighten me on how approve and allowance functions work using a usecase? I dont understand the underlying operations of these functions. Especially, when a token owner delegates the ...
- 25
1
vote
1
answer
172
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Metamask - get value entered from calling ERC20 "approve()" method
When we're asking a user to approve() the spending of a proprietary ERC20 Token for the first time (like say DAI, or SUSHI, etc.), the user has to enter the amount they're willing to approve - like ...
- 1,011
1
vote
1
answer
2k
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Is it possible for a contract to erc20 approve another contract?
I want my contract (#1) to be able to approve another contract (#2) to transfer erc20 tokens from #1 to #2. Is this possible?
- 463
1
vote
1
answer
75
views
Can approve function be malicious?
I'm so confused on how approve functions works:
If myToken contract has an approve function but the owner did not approve the contract B. Then contract B deploys a function and create a function that ...
- 89
1
vote
1
answer
88
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Invalid Permit Signature - Same Signature Generated by Different Address?
Our dApp uses Permit for gasless token approvals. We are generating a signature request with signTypedData, and it works except for a few strange occurrences where I am getting back an invalid ...
1
vote
1
answer
1k
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ERC20 Tax on sell (via swap)
I'm struggling with taxing upon swapping a token back for ETH. I can't figure out what I'm doing wrong here. I'm using Hardhat testnet forking Goerli to work with the Uniswap contracts. Also made ...
1
vote
4
answers
918
views
Allowing contract to take ERC20 tokens from msg.sender
I'm kind of new to Solidity and struggling with allowances and approvals. I want my smart contract to be allowed to take ERC20 tokens (LINK in this case) from the msg.sender. I'm using Remix on Goerli,...
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1
vote
2
answers
271
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How to set approval for all my erc 20 token on my marketplace smart contract
I am trying to build an nft marketplace where users buy nft using my own erc20 tokens. I want to eliminate the need for the user to set approval for the marketplace smart contract before they want to ...
- 9
1
vote
1
answer
2k
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Reverted with reason string 'ERC20: insufficient allowance'
I'm newbie on solidity and I'm trying a simple ERC20 on hardhat with task for understand use case
I follow this steps
Mint in owner
Owner owns N token
Owner would to approve Receiver for receive ...
1
vote
2
answers
2k
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How do you approve + transfer ERC20 tokens in 1 transaction?
I want to approve my tokens to allow a smart contract to transfer them for me to another contract.
Steps:
I approve my tokens for Contract A to spend on my behalf.
Contract A transfers my tokens to ...
- 544
1
vote
1
answer
740
views
Is "approve" required only for transferring tokens? Not a native coin?
Speaking of Ethereum blockchain, or any other one compatible with it: Polygon, Avalanche and others: is calling the function approve(...) mandatory only, and only, when there's a token involved in ...
- 35
1
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3
answers
1k
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What does web3's approve do before a token sell?
I'm trying to implement a bot with python and web3 from some code examples.
All of them call the approve function before selling a token? What is this function for and is it necessary?
Thanks
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1
vote
1
answer
787
views
delegatecall approve of an ERC20 contract
I try to call approve from a contract of another ERC20 contract:
The delegate call:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract Delegate {
address public constant f24 = ...
- 455
1
vote
3
answers
1k
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Why is there no approve function for MATIC token contract?
MATIC token is advertised as an ERC20 token. So why is there no approve function for MATIC token contract? https://polygonscan.com/address/0x0000000000000000000000000000000000001010#code
What is the ...
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1
vote
2
answers
2k
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Cant pass large uint in react.js (2**256-1) into solidity approve function
I am trying to call a simple approve() to allow my contract to spend my tokens.
Trying to make the amount argument = (2**256 - 1) however I am getting the below error message every time.
Unhandled ...
- 51
1
vote
1
answer
550
views
Approve and Swap/Deposit at the same time [duplicate]
So one of the most annoying things for me is having to Approve before calling Swap or Deposit.
I would love there to be a proxy contract which just calls Approve and Swap/Deposit in the same function.
...
- 315
1
vote
3
answers
5k
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IERC20.approve(spender, amount) thinks the owner is also the contract
I have these functions and deployed my contract to Ropsten testnet.
function setSmartContractAllownace(uint daiAmountIn) public {
IERC20 daiToken = IERC20(ropstenDAI);
daiToken.approve(...
1
vote
1
answer
3k
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Contract with function payable to receive ERC20 token in one shot?
I am trying to write a smart contract with a function that receives an ERC20 token (i.e.: DAI), but the transaction to call this function is always failing.
Let's assume I first record the ERC20 ...
- 3,399
1
vote
1
answer
930
views
How to make a delegatecall to external ERC20 token's approve function?
What I would like to do is something like this:
function testCall(uint amount) public virtual returns (bool) {
address tta = address(0xE7B6....);
(bool success, bytes memory result) = tta....
- 828
1
vote
1
answer
93
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Metatransaction EIP-712 compliant reverted on Tether USDT Polygon contract
I have a problem with the execution of a metatransaction EIP-712 compliant, I show you the backend code with ethers.js and the link of the contract on mainnet :slight_smile:
Contract : https://...
1
vote
2
answers
196
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Implementing an ERC20 Smart-Contract within another Smart-Contract
I’m trying to create a contract that lets people choose to pay for their transactions with either ETH, or another ERC20 Token - one that I’m creating and for now calling “DummyCoin”.
So basically when ...
- 1,011
1
vote
0
answers
191
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Can I cut a fee using multicall on Uniswap V3?
I developed my own frontend for Uniswap V3, and I was asking myself if I could cut a small fee of the input token using multicall.
Basically, I would calculate what 2 percent of the input token would ...
- 19
1
vote
1
answer
204
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TranferFrom in delegate call
I have an ERC20 test contract, also I did multicall with delegatecall function instead of call.
I have a three accounts: account1, account2, and account3.
account1 can spend tokens from account2 (I ...
- 25
1
vote
0
answers
322
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estimateGas with prerequisites (gas estimation requires approvals first)
I am trying to estimateGas for an Ethereum transaction with ethers signer.estimateGas(). This transaction should execute several trades on arbitrary DEXs.
To execute the transaction approvals of ERC-...
1
vote
1
answer
21
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What happened to these tokens?
I send some Matic token in one of my wallets to the other for cover fee of a transaction (0.05)matic
but as soon as transfer succeeded, this amount transferred to another address, without any approval ...
- 350
1
vote
2
answers
455
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giving contract permission to spend eth
Since eth does not have a contract address, how does one allow a contract to spend it. For example - I put in a swap request - 10 eth for its amount in usdt for example - could the contract spend my ...
user106332
1
vote
1
answer
1k
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Staking and ERC20 Approve (RPC Error: execution reverted: ERC20: transfer amount exceeds allowance)
I apologize if this question might seem a bit simple beforehand. I'm trying call the deposit function from my frontend, but it gives me the error mentioned above. I am confused as to if this is a ...
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