Check if wallet is approved to spend token

Moralis General
#1

Hi there,

I was wondering if there’s a way to check if a token is already approved for spending via Moralis API. I’m not asking how to approve the token for spending, I’ve figured that part out via reference: How to approve a token for spending on (Uniswap router contract). I’d like my script to check first before selling a token and then decide, based on the result, to either run approval first or skip it. That way it’s not approving a token that’s already approved every time it sells the same token. Thanks for your help.

#2

Hi,
It looks like this is what you need: https://deep-index.moralis.io/api-docs/#/token/getTokenAllowance

An example of requested url:
https://deep-index.moralis.io/api/v2/erc20/0x057Ec652A4F150f7FF94f089A38008f49a0DF88e/allowance?chain=eth&owner_address=0xd4a3BebD824189481FC45363602b83C9c7e9cbDf&spender_address=0x62AED87d21Ad0F3cdE4D147Fdcc9245401Af0044

#3

Nice! thanks man. So if allowance returns 0 it’s not been approved yet right?

#4

That should be the case, but you should test with a case where you know there is an approval.

#5

I see, ok so I’m getting the following error msg. Any ideas?..

chain = "bsc"
token = Web3.toChecksumAddress("0x40619dc9f00ea34e51d96b6ec5d8a6ad75457434")

contract = web3.eth.contract(token, abi=config.pancakeswapTokenAbi)
owner_address = contract.functions.owner().call()
apprvData = 'https://deep-index.moralis.io/api/v2/erc20/' + token + '/allowance?chain=' + chain + '&owner_address=' + owner_address + '&spender_address=' + config.walletAddress3 
apprvStatusReq = requests.request("GET", apprvData, headers=config.moralisAPI)
apprvStatus = apprvStatusReq.json()['allowance']
print(apprvStatus)

Error:

Traceback (most recent call last):
  File "c:/Users/Owner/Documents/BlockchainPy/MyCodes/scratchTest.py", line 28, in <module>
    apprvStatus = apprvStatusReq.json()['allowance']
KeyError: 'allowance'
#6

What you see if you print what is in apprvStatusReq.json()?

#7

Both
print(apprvStatusReq) and
print(apprvStatus) returns the same error as above

#8

That would be impossible for both of them to show the same error.

What does this code do?

print(apprvData)
apprvStatusReq = requests.request("GET", apprvData, headers=config.moralisAPI)
import json
print(json.dumps(apprvStatusReq.json(), indent=4)
#9

Pardon me, sir you’re right. To answer your previous question…it returned { } ( empty curly)

print(json.dumps(apprvStatusReq.json(), indent=4) also returned { }

1 Like
#10

I need an example of a contract, _owner and, _spender that has allowance in order to get you a working code example. You can also use directly web3 call to the contract to the allowance method in order to get that information.

#11

I got this working example for web3:

const CONTRACT_ADDRESS = CONTRACT_ADDRESS!!!!;

const abi = [{"constant":true,"inputs":[{"name":"_owner","type":"address"},{"name":"_spender","type":"address"}],"name":"allowance","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},]

let _owner = OWNER!!!!
let _spender = SPENDER!!!!
window.web3 = await Moralis.Web3.enable();
let contract_instance = new web3.eth.Contract(abi, CONTRACT_ADDRESS);
let x = await contract_instance.methods.allowance(_owner, _spender).call();
console.log(x);
#12

Sure, for example:

contract = 0x40619dc9F00ea34e51D96b6EC5d8a6aD75457434
owner = 0x29cdf45A1cda9Fd722108b05BaaA5785DF5E98aF
spender = 0xb5C2c0A73f59508731b915c646615089e1517628

Direct Web3 call in python would be ideal.

#13

python web3 example:

import json
import sys
from web3 import Web3

bsc = 'https://bsc-dataseed.binance.org/'
web3 = Web3(Web3.HTTPProvider(bsc))
print(web3.isConnected())


contract = '0x40619dc9F00ea34e51D96b6EC5d8a6aD75457434'
contract = web3.toChecksumAddress(contract)
abi = [{"constant":True,"inputs":[{"name":"_owner","type":"address"},{"name":"_spender","type":"address"}],"name":"allowance","outputs":[{"name":"","type":"uint256"}],"payable":False,"stateMutability":"view","type":"function"},]
contract = web3.eth.contract(address=contract, abi=abi)

_owner = web3.toChecksumAddress("0x29cdf45A1cda9Fd722108b05BaaA5785DF5E98aF")
_spender = web3.toChecksumAddress("0xb5C2c0A73f59508731b915c646615089e1517628")

x = contract.functions.allowance(_owner, _spender).call();
print(x)
1 Like
#14

Great! it works. However, I noticed that it returns 0 (zero) for both approved tokens and non-approved. I used pancakewap to confirm which tokens were approved or not. Any thoughts?

#15

For me it worked fine with approved tokens, as in returning a number and not 0.

#16

I copied and pasted the code, changed _owner to 3 other accounts that all belong to me, none of which returned anything besides a zero.

I also bought a new token and ran it before and after approving and it still returned a zero for both times. I don’t know anymore bro…

#17

send a DM in discord and I’ll give you a working example

#18

Ok what’s your handle on discord? Mine is BJ #6448

#19

Mine is Crypto Kid#9642

#20

You can find link for Moralis discord channel in https://admin.moralis.io/servers on the top of the page, in case that you are not already there.